^.H 


8^ 


^     H^/^p  </j(^ 


Issued  April  1-1, 1908. 


U.  S.  DEPARTMENT   OF  AGRICULTURE. 


FARMERS'    BULLETIN    No.  127. 


IMPORTANT  INSECTICIDES: 


DIRECTIONS  FOR  THEIR  PREPARATION  AND  USE. 


[Second  Revision.] 


C.  L.  MARLATT,  M.  S., 

ENTOMOLOGIST  AND   ASSISTANT  CHIEF,  BUREAU   OP  ENTOMOLOGY. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 
I  908. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  or  Entomology, 
Washington,  D.  C,  March  2,  190S. 
Sir:  I  have  the  honor  to  transmit  herewith  a  second  revision  of 
Farmers'  Bulletin  No.  127,  on  insecticides.    The  five  years  that  have 
elapsed  since  the  last  revision  of  this  publication  have  brought  some 
important  additions  to  our  knowledge  of  insecticides  and  have  neces- 
sitated some  changes  of  old  formulas.     These  additions  and  correc- 
tions have  been  incorporated  in  this  revision.     As  stated  in  the  letter 
of  transmittal  to  the  first  edition,  this  bulletin  supplants  Farmers' 
Bulletin  No.  19,  prepared  in  1894  by  Mr.  C.  L.  Marlatt,  then  First 
Assistant  Entomologist.    The  latter  publication,  having  gone  through 
four  slightly  revised  editions,  was  in  large  part  rewritten  by  Mr. 
Marlatt  early  in  1901  and  issued  under  the  new  number  to  take  the 
place  of  the  older  publication. 
Respectfully, 

L.  O.  Howard, 
Entomologist  and  Chief  of  Bureau, 
Hon.  James  Wilson, 

Secretary  of  Agriculture. 

127 

(2) 


CONTENTS. 


Page. 

Introductory 5 

Relation  of  food  habits  to  remedies 5 

Injury  from  biting  insects 5 

Injury  from  sucking  insects 6 

Groups  subject  to  special  treatment 7 

Insecticides  for  external  biting  insects  (food  poisons ) 7 

The  arsenicals 7 

Paris  green 8 

Copper  arsenite 8 

Arsenite  of  lime 9 

London  purple 9 

Arsenate  of  lead 9 

General  considerations 10 

How  to  apply  arsenicals 10 

The  wet  method 11 

The  dry  method 11 

Poisoned  bait 12 

Time  to  spray  for  biting  insects 13 

Care  in  the  use  of  arsenicals 14 

Insecticides  for  external  sucking  insects  (contact  poisons) 14 

Soaps  as  insecticides 15 

Pyrethrum,  or  insect  powder 16 

Tobacco  decoction 16 

Sulphur 16 

Petroleum  oils 17 

Pure  kerosene  treatment 18 

The  crude  petroleum  treatment 19 

The  oil-water  treatment 19 

Kerosene  emulsion  (soap  formula) 20 

Kerosene  emulsion  (milk  formula) 21 

The  distillate  emulsion 21 

How  to  use  the  emulsions 22 

Cautions  regarding  use  of  oil  washea 22 

Miscible  oils 23 

The  resin  wash 23 

The  lime-sulphur  wash 24 

Composition  and  preparation 25 

Directions  for  use 26 

Range  of  usefulness 26 

Time  to  spray  for  sucking  insects 27 

127 

(3) 


Page. 

Dusting  and  spraying  apparatus 28 

Powder  distributers , 28 

Liquid  sprayers 28 

The  barrel  pump 29 

Tank  outfits 29 

Geared  sprayers 29 

Gas-pressure  sprayers 29 

Hose,  nozzle,  and  agitator 30 

Selection  of  spraying  outfit 30 

Directions  for  spraying 31 

Hydrocyanic-acid  gas  treatment 31 

Fumigation  of  nursery  stock 32 

Orchard  fumigation 33 

Amounts  of  chemicals  to  use 33 

General  directions 35 

Construction  and  handling  of  tents 36 

Bisulpliid  of  carbon  vapor 38 

Remedies  for  subterranean  insects 38 

Hot  water 39 

Tobacco  dust 39 

Kerosene  emulsion  and  resin  wash 40 

Potash  fertilizers 41 

Bisulphid  of  carbon 41 

Submersion 42 

Remedies  for  insects  affecting  grain  and  other  stored  products 42 

General  methods  of  treatment 42 

Bisulphid  of  carbon 43 

Character  and  method  of  application 43 

Caution 44 

Sulphur  dioxid 44 

General  considerations  on  the  control  of  insects 45 

Advantage  of  prompt  treatment 45 

Killing  insects  as  a  profession 45 

Determination  of  the  result  of  treatment 46 

Control  of  insects  by  cultural  methods 47 

The  profit  in  remedial  measures 48 


ILLUSTRATIONS. 


Page. 

Fig.  1.  Illustrating  the  different  classes  of  biting  insects 6 

2.  Illustrating  the  different  classes  of  sucking  insects 6 

3.  Barrel  spray  jjump 28 

4.  Power  sprayer  at  work  in  apple  orchard 29 

5.  Vermorel  spray  nozzle  30 

6.  Tenting  trees  for  gas  treatment,  San  Diego,  Cal 32 

7.  Method  of  hoisting  sheet  tent 36 

127 


IMPORTANT  INSECTICIDES:  DIRECTIONS  FOR 
THEIR  PREPARATION  AND  USE. 


INTRODUCTORY. 

Without  going  minutely  into  the  fiekl  of  remedies  and  preventives 
for  insect  depredations  it  is  proposed  to  give  in  this  bulletin  brief 
directions  concerning  a  few  of  the  insecticide  agents  having  the  widest 
range  and  attended  with  the  greatest  usefulness,  economy,  and  ease 
of  ai^plication.  These  are  not  covered  by  patents,  and  in  general  it  is 
true  that  the  patented  articles  are  inferior,  many  of  the  better  of  them 
being  in  fact  mereh-^  more  or  less  close  imitations  of  the  standard 
substances  and  compounds  hereinafter  described.  Onl}^  such  brief 
references  to  food  and  other  habits  of  insects  will  be  included  as  are 
necessary  to  illustrate  the  principles  underlying  the  use  of  the  several 
insecticide  agents. 

RELATION  OF  FOOD  HABITS  TO  REMEDIES. 

For  the  intelligent  and  practical  employment  of  insecticides  it  is 
necessary  to  comprehend  the  nature  and  method  of  injury  commonly 
due  to  insects.  Omitting  for  the  present  purpose  the  exceptional 
forms  of  injury  which  necessitate  peculiar  methods  of  treatment,  the  ' 
great  mass  of  the  harm  to  growing  plants  from  the  attacks  of  insects 
falls  under  tAvo  principal  heads  based  on  distinct  principles  of  food 
economy,  viz,  whether  the  insect  is  a  biting  (mandibulate)  or  a  suck- 
ing (haustellate)  species.  Each  group  involves  a  special  system  of 
treatment. 

INJURY  FROM  BITING  INSECTS. 

The  biting  or  gnawing  insects  are  those  which  actually  masticate 
and  swallow  some  portion  of  the  solid  substance  of  the  plant,  as  the 
wood,  bark,  leaves,  flowers,  or  fruit.  They  include  the  majority  of  the 
injurious  larvae,  many  beetles,  and  the  grasshoppers.     (See  fig.  1.) 

127 

(5) 


For  these  insects  direct  poisons,  such  as  the  arsenicals,  which  may 
be  safel}^  applied  to  the  leaves  or  other  parts  of  the  plant  attacked, 


Fig.  1. — niustrating  the  dififerent  classes  of  biting  insects.   ^AU 
natural  size.      (Author's  illustration.) 

and  which  will  be  swallowed  by  the  insect  with  its 
food,  furnish  the  surest  and  simplest  remedy,  and 
should  always  be  employed,  except  where  the  parts 

treated  are  themselves  to  be  shortly  used  for  the  food  of  animals  or 

of  man. 

INJUHY  FROM  SUCKING  INSECTS. 

The  sucking  insects  are  those  which  injure  j^lants  by  the  gradual 
extraction  of  the  juices  from  the  bark,  leaves,  or  fruit,  and  include 
the  plant-bugs,  aphides,  scale  insects,  thrips,  and  plant-feeding  mites. 
These  insects  possess,  instead  of  biting  jaws,  sucking  beaks  or  bristles, 
which  are  thrust  down  through  the  outer  layers  of  the  bark  or  leaves 


Fia.  2. — Illustrating  the  different  classes  of  sucking  Insects.     Natural  size  and  enlarged. 

(Author's  illustration.) 

into  the  soft,  succulent  tissues  beneath  and  used  to  extract  the  jjlant 
juices,  with  a  resulting  injury  not  so  noticeable  as  in  the  first  group, 
but  not  less  serious.     (See  fig.  2.) 

127 


For  this  class  of  insects  the  application  of  poisons,  which  penetrate 
little,  if  at  all,  into  the  plant  cells,  is  of  trifling  value,  and  it  is  neces- 
sary to  use  substances  which  will  act  externally  on  the  bodies  of  these 
insects  as  a  caustic,  or  will  smother  or  stifle  them  by  closing  their 
breathing  pores,  or  will  fill  the  air  about  them  with  poisonous  fumes. 
Of  value  also  as  repellents  are  various  deterrent  or  obnoxious  sub- 
stances. 

Where  it  is  not  desirable  to  use  poisons  for  biting  insects  some  of 
the  means  just  enumerated  may  often  be  employed. 

GROUPS  SUBJECT  TO  SPECIAL  TREATMENT. 

The  two  general  groups  outlined  above  comprise  the  species  which 
live  and  feed  upon  the  exterior  of  plants  for  some  portion  or  all  of 
their  lives,  and  include  the  great  majority  of  the  injurious  species. 
Certain  insects,  however,  owing  to  peculiarities  of  habit,  inaccessi- 
bility, or  other  causes,  require  special  methods  of  treatment.  Of 
these,  two  groups  properly  come  within  the  scope  of  this  bulletin: 
(1)  Those  working  beneath  the  soil,  or  subterranean  insects,  such  as 
the  white  grubs,  root  maggots,  root  aphides,  etc.;  and  (2)  insects 
affecting  stored  products,  as  various  grain  and  flour  pests. 

T.hree  other  groups,  which  include  species  requiring  very  diverse 
methods  of  treatment,  and  which  are  not  considered  in  this  bulletin, 
are  (1)  such  internal  feeders  as  wood,  bark,  and  stem  borers,  leaf 
miners,  and  gall  insects,  and  species  living  within  fruits;  (2)  house- 
hold pests;  and  (3)  animal  parasites. 

The  classification  of  insects  outlined  above,  based  on  mode  of  nour- 
ishment, and  indicating  groups  amenable  to  similar  remedial  treat- 
ment, simply  stated,  is  as  follows: 

I.  Elxternal  feeders :  III.  Subterranean  insects. 

(a)  Biting  insects.  IV.  Insects  affecting  stored  products. 

(&)   Sucking  insects.  V.  Household  pests. 

II.  Internal  feeders.  VI.  Animal  parasites. 

INSECTICIDES  FOE  EXTERNAL  BITING  INSECTS  (FOOD  POISONS) . 

THE  ARSENICALS. 

The  arsenical  compounds  have  supplanted  practically  all  other 
substances  for  insects  falling  under  this  heading.  Of  these,  Paris 
green  is  the  best  known  and  most  generally  emploj'^ed,  and  probably 
from  2,000  to  3,000  tons  of  it  are  used  for  horticultural  purposes 
every  year.  Arsenate  of  lead  is  a  new  arsenical  coming  into  very 
general  use,  and  arsenite  of  copper,  a  near  ally  of  Paris  green,  is  also 
increasingly  employed.  Arsenite  of  lime  is  usually  a  home  prepara- 
tion, and  London  purple,  the  least  uniform  in  composition  of  all  the 
mixtures,  is  rather  going  out  of  use.     The  powdered  white  arsenic  or 

127 


8 

arsenious  oxide  can  not  be  employed  on  account  of  its  scalding  action 
on  the  foliage,  and  in  the  case  of  any  of  the  arsenicals  the  percentage 
of  soluble  arsenic  (arsenious  oxide)  should  be  at  the  very  minimum, 
certainly  not  in  excess  of  3  or  4  per  cent.  With  more  than  4  per  cent 
soluble  arsenic  there  is  great  danger  of  scalding  the  foliage,  the 
danger  increasing  with  the  percentage  of  soluble  arsenic." 

Paris  green. — Paris  green  is  a  definite  chemical  compound  of  white 
arsenic,  copper  oxide,  and  acetic  acid,  and  is  known  as  the  aceto- 
arsenite  of  copper.  Properly  compounded  and  washed,  it  should  be 
substantially  uniform  in  composition  and  nearly  free  from  uncom- 
bined  soluble  white  arsenic.  It  is  a  rather  coarse  powder,  or,  more 
properly  speaking,  crystal,  and  settles  rapidly  in  water,  which  is  its 
gi-eatest  fault.  To  give  better  suspension  in  water,  it  should  be  re- 
duced to  such  fineness  by  grinding  that  it  will  pass  through  a  100-mesh 
sieve.  Its  high  cost  (varying  from  20  to  40  cents  a  pound,  following 
the  market  price  of  copper  and  arsenic)  is  further  increased  by  its 
being  crystallized  with  acetic  acid,  making  it  a  more  brilliant  pigment, 
but  giving  it  a  coarse  grain  and  rendering  it  a  poorer  insecticide.  The 
standards  of  purity  demanded  by  various  States  have  led  most  manu- 
facturers to  produce  a  very  fair  article,  but  if  there  is  any  doubt  of 
purity  a  sample  should  be  submitted  to  the  State  Experiment  Station 
or  to  the  United  States  Department  of  Agriculture  for  analysis. 

Copper  arsenite. — Copper  arscnite,  often  called  Scheele's  green,  is 
the  simple  arsenite  of  copper,  differing  from  Paris  green  in  lacking 
acetic  acid.  It  is  a  much  finer  powder  than  Paris  green  and  therefore 
is  more  easily  kept  in  suspension,  and  it  costs  considerably  less  per 
pound.  It  is  dull  in  color,  lacking  the  brilliancy  of  Paris  green. 
When  properly  prepared  and  washed  by  the  manufacturers,  it  is  no 
more  harmful  to  the  foliage  than  Paris  green  when  the  latter  is 
brought  to  an  equal  fineness,  and  should  supplant  the  latter  as  an 
insecticide.  It  is  used  in  the  same  way  and  at  about  the  same  strength 
as  Paris  green. 

<^  Hellehore. — The  powdered  roots  of  the  white  hellebore  {Veratrum  viride) 
are  often  recommended  and  used  as  an  insecticide,  particularly  as  a  substitute 
for  the  arsenites.  This  substance  is  useful  when  a  few  plants  only  are  to  be 
sprayed,  as  in  yards  and  small  gardens,  but  is  too  expensive  for  large  opera- 
tions. It  kills  insects  in  the  same  way  as  the  arsenicals,  as  an  internal  poison, 
and  is  less  dangerous  to  man  and  the  higher  animals ;  but  if  a  sufficient  amount 
be  taken  it  will  cause  death.  It  is  particularly  effective  against  the  larva;  of 
sawflies,  such  as  the  cherry  slug,  rose  slug,  currant  worms,  and  strawberry 
worms. 

It  may  be  applied  as  a  dry  powder,  preferably  diluted  with  from  5  to  10  parts 
of  flour,  and  dusted  on  the  plants  through  a  muslin  bag  or  with  powder  bellows. 
The  application  should  be  made  in  the  morning,  when  the  plants  are  moist  with 
dew.  Used  as  a  wet  application,  it  should  be  mixed  with  water  in  the  propor- 
tion of  1  ounce  to  the  gallon  of  water  and  applied  as  a  spray. 
127 


Arsenite  of  lime. — This  is  normally  a  home-made  preparation,  and 
there  is  no  reason  for  its  not  being  employed  wherever  one  is  willing 
to  take  the  trouble  to  compound  it  carefully.  Its  preparation,  de- 
scribed below,  following  substantially  the  Kedzie  formula,  is  simple 
enough : 

White  arsenic pounds__       1 

CiTstal  sal  soda" do 4 

y/ater  i gallons.-       1 

Place  the  above  ingredients  in  an  iron  vessel,  which  is  to  be  kept 
exclusively  for  this  purpose,  and  boil  for  twenty  minutes  or  until 
dissolved.  To  40  or  50  gallons  of  water  a  pint  of  this  stock  solution 
and  3  to  4  pounds  of  freshly  slaked  lime  are  added.  This  excess 
of  liine  not  only  takes  up  any  free  arsenic,  but  by  its  distribution  on 
the  foliage  enables  one  to  determine  how  well  the  spraying  has  been 
done.  This  formula  has  been  thoroughly  tested  and  used  now  for 
many  years,  and  is  fully  as  efficient  as  any  other  arsenical  and  far 
cheaper.  Chemically  it  is  arsenite  of  lime.  The  soda  is  used  to 
hasten  the  process  and  to  insure  the  combination  of  all  the  arsenic 
with  the  lime.  The  greatest  care  should  be  exercised  in  preparing 
the  stock  mixture,  and  afterwards  it  should  be  plainly  labeled  to  pre- 
vent its  being  mistaken  for  some  other  substance.  The  only  objec- 
tion to  its  use  is  the  necessity  of  handling  the  poisons  in  its  home 
preparation. 

London  purple. — London  purple  is  a  waste  product  in  the  manufac- 
ture of  aniline  dyes  and  contains  a  nmnber  of  substances,  the  chief 
of  which  are  white  arsenic  and  lime.  It  is  not  so  effective  as  the 
copper  arsenites,  and  contains  a  much  larger  percentage  of  soluble 
arsenic,  and  is  very  apt  to  scald  foliage  unless  very  carefully  mixed 
with  fresh  stone  lime.  It  comes  as  a  very  fine  powder,  and  is  easily 
kept  in  suspension.  It  costs  about  10  cents  a  pound.  If  employed, 
the  lime  should  always  be  added. 

Arsenate  of  lead. — Arsenate  of  lead  may  be  prepared  at  home  by 
combining  approximately  3  parts  of  the  crystallized  arsenate  of  soda 
with  7  parts  of  crystallized  acetate  of  lead  (sugar  of  lead)  in  water. 
This  gives  a  slight  excess  of  acetate  of  lead.  Each  of  the  ingredients 
should  be  dissolved  separately  in  water  in  wooden  vessels,  and  the 
two  solutions  poured  together  into  the  spray  tank  filled  with  water. 
The  white,  flocculent  precipitate  of  arsenate  of  lead  which  im- 
mediately results  is  extremely  fine  and  remains  in  suspension  much 
longer  than  any  other  arsenical.  Furthermore,  prepared  in  this  way 
and  diluted  at  once,  there  is  secured  a  mixture  that  is  chemically  su- 
perior to  the  combined  product  sold  in  paste  form  and  that  remains  in 

<^Two  pounds  only  of  the  anhydrous  sal  soda  are  necessary. 
73159— Bui.  127—09 2 


10 

jiuspension  better.  Arsenate  of  soda  costs  wholesale  about  10  cents  a 
pound,  and  first-class  acetate  of  lead  about  10  cents  a  j^ound. 

Arsenate  of  lead  may  be  used  at  any  strength  from  3  to  15  pounds 
to  100  gallons  of  "svater  without  injury  to  the  foliage,  for  the  reason 
that  it  contains  little,  if  any,  soluble  arsenic.  It  is  ordinarily  used 
at  the  rate  of  4  to  G  pounds  to  the  100  gallons  of  water  or  Bordeaux 
mixture.  In  later  years  it  has  come  into  general  use,  especially  for 
spraying  plants  sensitive  to  arsenical  poisoning,  such  as  peach,  and 
also  in  cases  where  it  is  necessary  to  make  heavy  applications.  Its 
safety  as  regards  the  burning  of  foliage  and  its  adhesive  quality 
offset  its  greater  cost,  and  it  is  now  much  used  in  the  codling  moth 
•work  and  general  arsenical  spraying. 

In  the  home  preparation  of  this  arsenical,  the  number  of  pounds 
of  the  poison  per  100  gallons  of  water  as  given  in  directions  for  use 
should  be  understood  to  mean  the  combined  weights  of  the  two 
ingredients.  In  point  of  fact,  the  resulting  lead  arsenate  is  only 
about  half  the  actual  weight  of  the  two  ingredients,  which  explains 
in  part  the  apparently  excessive  amounts  used  as  compared  with 
other  arsenicals. 

A  good  many  brands  of  arsenate  of  lead  can  be  purchased  on  the 
market,  usually  in  the  form  of  heavy  pastes.  As  already  indicated, 
they  have  not  the  same  power  of  remaining  in  suspension  as  the 
freshly  made  product,  but  are  otherwise,  if  properly  made,  quite 
satisfactory.  The  water  content,  which  is  variable,  should  be  spe- 
cifically indicated  and  guaranteed,  to  make  it  possible  to  use  the 
poison  at  the  strength  desired. 

Arsenite  of  lead  is  a  compound  very  similar  to  the  arsenate  of  lead, 
but  it  contains  a  less  percentage  of  arsenic.  It  is  prepared  from 
sodium  arsenite. 

General  considerations. — In  point  of  solubility  and  corresponding 
danger  of  scalding  the  foliage,  these  arsenicals  fall  in  the  following 
order,  the  least  soluble  first:  Arsenate  of  lead,  arsenite  of  lime,  Paris 
green,  copper  arsenite,  and  London  purple.  In  point  of  cost  the 
arsenite  of  lime  is  much  cheaper  than  the  other  arsenicals,  and  the 
arsenate  of  lead,  at  the  rate  at  which  it  is  necessary  to  use  it,  much  the 
most  expensive.  But  after  all  the  main  cost  is  in  the  application, 
and  it  is  therefore  well  worth  while  to  secure  a  good  arsenical  and 
get  the  best  results. 

HOW  TO  APPLY  ABSENICALS. 

There  are  three  principal  methods  of  applying  arsenicals.  The  wet 
method,  which  consists  in  using  these  poisons  in  water  in  the  form  of 
spray,  is  the  standard  means,  secures  uniform  results  at  least  expense, 
and  is  the  only  practical  method  of  protecting  fruit  and  shade  trees. 

127 


11 

The  dry  application  of  these  poisons  in  the  form  of  a  powder,  which  is 
dusted  over  plants,  is  more  popular  as  a  means  against  the  cotton 
worm  in  the  South,  where  the  rapidity  of  treatment  possible  by  this 
method,  and  its  cheapness,  give  it  a  value  against  this  insect,  in  the 
practical  treatment  of  which  prompt  and  economical  action  are  the 
essentials.  This  method  is  also  feasible  for  any  low-growing  crop, 
such  as  potatoes,  young  cabbages,  or  other  plants  not  to  be  immedi- 
ately employed  as  food.  The  third  method  consists  in  the  use  of 
the  arsenicals  in  the  form  of  poisoned  baits,  and  is  particularly  avail- 
able for  such  insects  as  cutworms,  wureworms,  and  grasshoppers  in 
local  invasions. 

The  wet  method.— Either  Paris  green,  arsenite  of  copper,  arsenite  of 
lime,  or  London  purple  may  be  used  at  the  rate  of  1  pound  of  the 
poison  to  100  to  250  gallons  of  water,  or  1  ounce  to  G  to  15  gallons. 
The  stronger  mixtures  are  for  such  vigorous  foliage  as  that  of  the 
potato,  and  the  greater  dilutions  for  the  more  tender  foliage  of  the 
peach  or  plum.  An  average  of  1  pound  to  150  gallons  of  water  is  a 
good  strength  for  general  purposes.  The  poison  should  first  be  made 
into  a  thin  paste  in  a  small  quantity  of  water  and  quicklime  added  in 
amount  equal  to  the  poison  used,  to  take  up  the  free  arsenic  and 
remov^e  or  lessen  the  danger  of  scalding.  An  excess  of  lime  will  do 
no  injury.  The  poisons  thus  mixed  should  be  strained  into  the  spray 
tank  or  reservoir,  care  being  taken  that  all  the  poison  is  pulverized 
and  washed  through  the  meshes  of  the  strainer.  The  use  of  the  lime 
is  especially  desirable  in  the  case  of  the  peach  and  plum,  the  foliage 
of  which,  particularly  the  former,  is  very  tender  and  easily  scalded. 
To  the  stronger  foliage  of  the  apple  and  m.ost  shade  trees  Paris  green 
may  be  applied  without  danger  at  the  strength  of  1  pound  to  150  gal- 
lons of  water ;  with  London  purple  it  is  always  better  to  use  the  lime. 
The  method  of  preparation  of  arsenate  of  lead  has  already  been  indi- 
cated.    Lime  is  not  needed  with  this  arsenical. 

If  it  be  desirable  to  apply  a  fungicide  at  the  same  time,  as  on  the 
apple  for  the  codling  moth  and  the  apple  scab  fungus,  the  Bordeaux 
mixture  "  may  be  used  instead  of  water,  adding  the  arsenical  to  it  at 
the  same  rate  per  gallon  as  when  water  is  used.  The  lime  in  this  fun- 
gicide neutralizes  any  excess  of  free  arsenic  and  makes  it  an  excellent 
medium  for  the  arsenical,  as  it  removes  liability  of  scalding  the  foli- 
age and  permits  an  application  of  the  arsenical,  if  necessary,  eight  or 
ten  times  as  strong  as  it  could  be  employed  with  water  alone. 

The  arsenicals  can  not  be  safely  used  with  most  other  fungicides, 
such  as  the  sulphate  of  copper,  eau  celeste,  or  iron  chloride  solution, 
the  scalding  effects  of  these  being  greatly  intensified  in  the  mixture. 

The  dry  method. — The  following  description  applies  to  the  pole- 

«*  See  F.  B.  243,  Fungicides  and  Their  Use  in  Preventing  Diseases  of  Fruits. 
127 


12 

and-bag  duster  commonly  used  against  the  cotton  worm:  A  pole  5 
to  8  feet  long  and  about  2  inches  in  diameter  is  taken,  and  a  three- 
fourths-inch  hole  bored  through  it  within  6  inches  of  each  end. 
Near  each  end  is  securely  tacked  a  bag  of  "  8-ounce  osnaburg  cloth," 
1  foot  wide  and  18  inches  to  2  feet  long,  so  that  the  powdered  poison 
may  be  introduced  into  the  bags  with  a  funnel  through  the  holes  at 
the  ends  of  the  pole.  The  bags  are  filled  with  undiluted  Paris  green, 
which  is  generall}^  preferred  to  London  purple  on  account  of  its 
quicker  action,  and  the  apparatus  is  carried  on  horse  or  mule  back, 
through  the  cotton  fields,  dusting  two  or  four  rows  at  once.  The 
shaking  induced  b}^  the  motion  of  the  animal  going  at  a  brisk  walk 
or  at  a  trot  is  sufficient  to  dust  the  plants  thoroughly,  or  the  pole  may 
be  jarred  by  hand.  The  application  is  preferably  made  in  early 
morning  or  late  evening,  when  the  dew  is  on,  to  cause  the  poison  to 
adhere  better  to  the  foliage. 

From  1  to  2  pounds  are  required  to  the  acre,  and  from  10  to  20 
acres  are  covered  in  a  day.  The  occurrence  of  heavv-  rains  may  neces- 
sitate a  second  application,  but  frequently  one  will  suflfice.  This 
simple  apparatus,  on  account  of  its  effectiveness  and  cheapness,  is 
employed  throughout  the  cotton  belt  to  the  general  exclusion  of  more 
complicated  and  expensive  machinery.  The  cost  frequently  does  not 
exceed  25  cents  per  acre,  and  the  results  are  so  satisfactory  that  the 
leaf  worm  is  no  longer  considered  a  serious  factor  in  cotton  culture. 

With  the  patented  air-blast  machines  for  the  dry  distribution  of 
poisons,  arsenicals  are  diluted  with  10  parts  of  flour,  lime,  or  ground 
gypsum,  and  from  60  to  75  acres  may  be  covered  in  a  day  by  using 
relays  of  men  and  teams.  Greater  uniformity  is  secured  with  these 
machines  in  distribution  of  the  poisons,  but  their  cost  (from  $30  to 
$60)  prevents  their  general  use. 

The  planter  should  have  a  good  supply  of  poison  on  hand  and  appa- 
ratus for  its  application  prepared  in  advance,  since  when  the  worm 
puts  in  an  appearance  its  progress  is  very  rapid,  and  a  delay  of  a 
single  day  may  result  in  material  damage  to  the  crojo. 

If  small  garden  patches  are  dusted  with  poison  by  this  or  similar 
means  from  bags  or  with  hand  bellows,  it  is  advisable  always  to  dilute 
the  poison  with  10  parts  of  flour,  or  f)referably  lime,  and  for  applica- 
tion to  vegetables  which  ultimately  will  be  used  for  food,  as  the  cab- 
bage, 1  ounce  of  the  poison  should  be  mixed  with  6  pounds  of  flour  or 
10  of  lime  and  dusted  merely  enough  to  show  evenly  over  the  surface. 
Arsenicals  should  not  be  applied  to  lettuce  or  other  vegetables  the 
free  leafage  of  which  is  eaten. 

Poisoned  bait. — It  is  not  always  advisable  or  effective  to  apply 
arsenicals  directly  to  the  plants,  and  this  is  particularly  true  in  rela- 
tion to  the  attacks  of  the  grasshopper  and  of  the  various  cutworms 

127 


13 

and  wireworms.  In  such  cases  the  use  of  poisoned  bait  has  proved 
very  satisfactory. 

For  grasshoppers,  take  1  part,  by  weight,  of  white  arsenic,  1  of 
sugar,  or  mohisses,  and  6  of  bran,  to  which  add  water  to  make  a  wet 
mash.  Place  a  tablespoonfiil  of  this  at  the  base  of  each  tree  or 
vine,  or  apply  a  line  of  baits  just  ahead  of  the  advancing  army  of 
grasshoppers,  placing  a  tablespoonful  of  the  mash  every  6  or  8  feet 
and  following  up  with  another  line  behind  the  first. 

A  cheap  grasshopper  bait  used  successfully  in  parts  of  the  West 
is  obtained  by  mixing  fresh  horse  droppings  with  arsenicals.  One 
pound  of  Paris  green,  or  some  other  convenient  arsenical,  together 
with  2  pounds  of  salt,  are  thoroughly  mixed  with  60  pounds  of  fresh 
horse  droppings.  The  resulting  mixture  is  scattered  among  the  young 
"  hoppers  "  or  around  the  edges  of  fields  which  it  is  thought  may  be 
invaded.  A  very  convenient  receptacle  in  which  to  make  this  prepa- 
ration is  a  half  barrel.  A  trowel  or  paddle  can  be  used  in  scattering 
the  mixture  in  the  desired  places. 

Bran  and  Paris  green,  on  the  authority  of  Prof.  J.  B.  Smith,  thor- 
oughly mixed  and  sprinkled  dry  on  cabbage  heads,  proved  a  most 
successful  remedy  for  cabbage  worms,  the  latter  preferring  the 
poisoned  bran  tc  the  cabbage,  to  their  prompt  undoing.  The  same 
dry  mixture  has  been  successfully  employed  against  cutworms  and  is 
recommended  by  Smith  for  the  army  worm,  running  it  in  rows  10 
feet  apart  across  the  infested  field.  One  pound  of  jDoison  to  10  of 
bran  is  a  good  proportion.  The  bran-arsenic  bait  may  also  be  used 
for  cutworms. 

For  sowbugs,  or  pill  bugs,  which  frequently  are  injurious  pests  to 
tender  flowering  plants  and  vegetables  grown  under  frames  or  in 
glass  houses,  poisoned  slices  of  potato  have  proved  to  be  the  most 
effectual  remedy.  The  freshly  sliced  potato  may  be  poisoned  by  dip- 
ping in  a  strong  arsenical  solution,  or  by  dusting  thickly  with  a  dry 
arsenical,  and  should  then  be  distributed  over  the  beds.  Pansy  beds 
have  been  notably  protected  in  this  way,  and  a  Michigan  vegetable 
grower  reports  that  in  two  nights  he  destro3'ed  upward  of  24,000  of 
these  bugs  by  this  means  in  four  houses  used  for  lettuce  growing. 

Another  remedy  for  cutworms  and  also  for  wircworn-s  is  poisoned 
green  succulent  vegetation,  such  as  freshly  cut  clover,  distributed  in 
small  bunches  in  the  infested  fields.  Dip  the  bait  in  a  very  strong 
arsenical  solution,  and  protect  it  from  drying  by  covering.  Renew 
the  bait  as  often  as  it  becomes  dry,  or  every  three  to  five  days. 

TIME  TO  SPRAY  FOR  BITING  INSECTS. 

Specific  directions  for  spraying  with  arsenicals  to  control  im- 
portant insect  pests  are  given  in  Farmers'  Bulletins  or  in  circulars 
of  this  Bureau  relating  to  these  different  insects.    One  of  the  princi- 

127 


14 

pal  uses  of  arsenical  poisons  is  for  the  control  of  the  codling  moth. 
Detailed  information  on  the  subject  is  given  in  Farmers'  Bulletins 
Nos.  247  and  283.  The  plum  curculio  is  discussed  in  Circular  No.  73, 
and  leaf -feeding  grape  insects  in  Farmers'  Bulletin  No.  284.  Other 
publications  relating  to  special  insect  problems  are  also  available 
giving  detailed  directions  for  spraying. 

For  leaf-feeding  insects  in  general,  such  as  the  Colorado  potato 
beetle,  blister  beetles,  elm  leaf-beetle,  maple  Avorm,  and  other  forest 
or  shade-tree  caterpillars,  the  application  should  be  mads  at  the 
earliest  indication  of  injury,  and  repeated  as  often  as  necessary. 
Fruit  trees  should  never  be  sprayed  when  in  bloom,  on  account  of 
the  liability  of  poisoning  honey  bees  or  other  insects  useful  as  cross- 
fertilizers. 

There  is  no  basis  for  the  idea  occasionally  advanced  that  the  fre- 
quent use  of  Paris  green  or  other  arsenicals  on  potatoes  and  other 
crops  is  injurious  to  the  foliage  or  health  of  the  treated  plants.  This 
matter  has  been  fully  tested,  and  the  injurious  results  can  always 
be  accounted  for  by  improper  mixtures  or  applications. 

CARE   IN   THE   USE   OF   AUSENICALS. 

It  must  be  remembered  that  these  arsenicals  are  very  poisonous  and 
should  be  so  labeled.  If  ordinary  precautions  are  taken,  there  is  no 
danger  to  man  or  team  attending  their  application.  The  wetting  of 
cither,  which  can  not  always  be  avoided,  is  not  at  all  dangerous,  on 
account  of  the  great  dilution  of  the  mixture,  and  no  ill  effects  what- 
ever have  resulted  from  this  source.  With  some  indi\'i duals  the  arsen- 
ate of  lead,  when  in  strong  mixture,  affects  the  eyes,  but  this  is  im- 
usual,  and,  with  a  little  care  in  spraying,  the  mist  need  not  strike  the 
operator  at  all. 

The  poison  disappears  from  the  plants  almost  completely  within 
twenty  to  twent3'-five  days,  and  even  if  the  plants  were  consumed 
shortly  after  the  application,  an  impossible  quantity  would  have  to  be 
eaten  to  get  a  poisonous  dose.  To  illustrate,  in  the  case  of  the  apple, 
if  the  entire  fruit  were  eaten,  core  and  all,  it  would  take  several  bar- 
rels at  a  single  sitting  to  make  a  poisionous  dose  (Riley),  and  with  the 
cabbage,  dusted  as  recommended  above,  28  heads  would  have  to  be 
eaten  at  one  meal  to  reach  this  result  (Gillette).  It  is  preferable, 
however,  to  use  other  insecticides  in  the  case  of  vegetables  soon  to  be 
eaten,  and  thus  avoid  all  appearance  of  danger. 

INSECTICIDES  FOR  EXTERNAL  SUCKING  INSECTS  (CONTACT 

POISONS). 

The  simple  remedies  for  this  class  of  insects,  such  as  soap,  insect 
pov.'der,  sulphur,  tobacco  decoction,  etc.,  are  frequently  of  value,  but 
need  little  special  explanation.     Some  brief  notes  will  be  given,  how- 

127 


15 

ever,  describing  the  methods  of  using  some  of  these  substances  which 
are  easily  available  and  will  often  be  of  service,  particularly  where 
few  plants  are  to  be  treated.  The  standard  remedies  for  this  group 
of  insects,  viz,  crude  petroleum,  kerosene,  and  kerosene  emulsions, 
resin  washes,  lime-sulphur  wash,  hydrocyanic  acid  gas,  and  vapor  of 
bisulphid  of  carbon,  will  be  treated  farther  on, 

SOAPS   AS    INSECTICIDES. 

Any  good  soap  is  effective  in  destroying  soft-bodied  insects,  such  as 
aphides  and  3'oung  or  soft-bodied  larvae.  As  winter  washes  in  very 
strong  solution,  they  furnish  one  of  the  safest  and  most  effective  means 
against  scale  insects.  The  soaps  made  of  fish  oil  and  sold  under  the 
name  of  whale-oil  soaps  are  often  especially  valuable,  but  they  are 
variable  in  composition  and  merits.  A  soap  made  with  caustic  potash 
rather  than  with  caustic  soda  which  is  commonly  used,  and  not  con- 
taining more  than  30  per  cent  of  water,  should  be  demanded,  the  jDot- 
ash  soap  yielding  a  liquid  in  dilution  more  readily  sprayed  and  more 
effective  against  insects.  The  soda  soap  washes  are  apt  to  be  gelatin- 
ous when  cold,  and  difficult  or  impossible  to  spray  except  when  kept 
at  a  very  high  temperature. 

For  aphides  and  delicate  larvae,  such  as  the  pear  slug,  a  strength 
obtained  by  dissolving  half  a  pound  of  soap  in  a  gallon  of  water  is 
sufficient.  For  the  pea  aphis  as  little  as  1  pound  of  potash  fish-oil 
soaj)  to  G  gallons  has  been  effective.  Soft  soap  will  answer  as  well 
as  hard,  but  at  least  double  quantity  should  be  taken. 

As  a  winter  wash  for  the  San  Jose  and  allied  scale  insects,  whale-oil 
or  fish-oil  soap  is  dissolved  in  water  by  boiling  at  the  rate  of  2  pounds 
of  soap  to  the  gallon  of  water.  If  applied  hot  and  on  a  comparatively 
warm  day  in  winter,  it  can  be  easily  put  on  trees  with  an  ordinar}'' 
spray  pump.  On  a  very  cold  day,  or  with  a  cold  solution,  the  mix- 
ture will  clog  the  pump  and  difficulty  will  be  experienced  in  getting  it 
on  the  trees.  Trees  should  be  thoroughly  coated  with  this  soap  wash. 
Pear  and  apple  trees  may  be  sprayed  at  any  time  during  the  winter. 
Peach  and  plum  trees  are  best  sprayed  in  the  spring,  shortly  before 
the  buds  swell.  If  sprayed  in  midwinter  or  earlier,  the  soap  solution 
seems  to  prevent  the  development  of  the  fruit  buds,  and  a  loss  of  fruit 
for  one  year  is  apt  to  be  experienced,  the  trees  leafing  out  and  grow- 
ing, however,  perhaps  more  vigorously  on  this  account.  The  soap 
treatment  is  perfectly  safe  for  all  kinds  of  trees,  and  is  very  effective 
against  the  scale.  With  large  trees,  or  badly  infested  trees,  as  a  pre- 
liminary to  treatment,  it  is  desirable  with  this  as  well  as  other  appli- 
cations to  i^rune  them  back  very  rigorously.  This  results  in  an  econ- 
omy of  spray  and  makes  much  more  thorough  and  effective  work 
possible.     The  soap  can  be  secured  in  large  quantities  at  from  3^ 

127 


16 

cents  to  4  cents  a  pound,  making  the  mixture  cost,  as  applied  to  the 
trees,  ftx)m  7  cents  to  8  cents  a  gallon. 

PYRETHRUM,  OR  INSECT  POWDER. 

This  insecticide  is  sold  under  the  names  of  Buhach,  Dalmatian,  and 
Persian  insect  powder,  or  simply  insect  powder,  and  is  the  ground-up 
flowers  of  the  Pyrethrum  plant.  It  acts  on  insects  externally  through 
their  breathing  pores,  and  is  fatal  to  many  forms  both  of  biting  and 
sucking  insects.  It  is  not  poisonous  to  man  or  the  higher  animals, 
and  hence  may  be  used  where  poisons  would  be  objectionable.  Its 
chief  value  is  against  household  pests,  such  as  roaches,  flies,  and  ants, 
and  in  greenhouses,  conservatories,  and  small  gardens,  where  the  use 
of  arsenical  poisons  would  be  inadvisable. 

It  is  used  as  a  dry  powder,  pure  or  mixed  with  flour,  in  which  form 
it  may  be  puffed  about  rooms  or  over  plants.  On  the  latter  it  is 
preferably  applied  in  the  evening,  so  as  to  be  retained  by  the  dew .  To 
keep  out  mosquitoes,  and  also  to  kill  them,  burning  the  powder  in  a 
tent  or  room  w^ill  give  satisfactory  results. 

It  may  also  be  used  as  a  spray  at  the  rate  of  1  ounce  to  2  gallons  of 
water,  but  in  this  case  should  be  mixed  some  twenty-four  hours  before 
being  ajjplied.  For  immediate  use,  a  decoction  may  be  prepared  by 
boiling  in  water  from  five  to  ten  minutes. 

TOBACCO  DECOCTIOU. 

A  tobacco  decoction  sufficiently  strong  for  aphides  and  other  very 
delicate  insects  may  be  prepared  from  tobacco  stems  and  other  refuse 
tobacco  by  boiling  at  the  rate  of  1  pound  for  each  1  or  2  gallons  of 
water,  sufficient  water  being  added  to  make  up  for  that  lost  in  boiling. 

SULPHUR. 

Flowers  of  sulphur  is  one  of  the  best  remedies  for  plant  mites,  such 
as  the  red  spider,  the  six-spotted  orange  mite,  and  the  rust  mite  of 
citrus  fruits.  It  may  be  applied  in  several  forms,  the  simplest  of 
which  is  its  use  as  a  dry  povv'der  dusted  over  the  trees  with  powder 
bellows  or  any  broadcasting  device,  preferably  in  the  early  morning 
when  the  foliage  is  damp  with  dew,  or  immediately  after  a  rain.  For 
the  rust  mite  in  very  moist  climates,  such  as  that  of  Florida,  to  keep 
the  fruit  bright  it  is  sufficient  merely  to  sprinkle  the  sulphur  about 
under  the  trees.  The  flowers  of  sulphur  may  be  easily  ajDplied  also 
with  any  other  insecticide,  such  as  kerosene  emulsion,  resin  wash,  or 
a  soap  w\ash,  mixing  it  up  first  into  a  paste  and  then  adding  it  to  the 
spray  tank  at  a  rate  of  from  1  to  2  pounds  to  50  gallons. 

Somewhat  more  uniform  results  can  be  obtained  perhaps  b}^  getting 
the  sulphur  into  solution,  either  dissolving  it  with  lye  or  by  boiling 
it  with  lime. 

127 


17 

In  making  the  lye-sulphiir  wash,  first  mix  20  pounds  of  flowers  of 
sulphur  into  a  paste  with  cold  water,  then  add  10  pounds  of  pulver- 
ized caustic  soda  (98  per  cent).  The  dissolving  lye  will  boil  and 
liquefy  the  sulphur.  "Water  must  be  added  from  time  to  time  to  pre- 
vent burning,  until  a  concentrated  solution  of  20  gallons  is  obtained. 
Two  gallons  of  this  is  sufficient  for  50  gallons  of  spray,  giving  a 
strength  of  2  pounds  of  sulphur  and  1  of  lye  to  50  gallons  of  water. 
An  even  stronger  application  can  be  made  without  danger  to  the 
foliage.  This  mixture  can  also  be  used  in  combination  with  other 
insecticides. 

The  chemical  combination  of  sulphur  and  lime  known  as  sulphid 
of  lime  is  perhaps  a  better  liquid  sulphur  solution  than  the  last  as  a 
remedy  for  mites.  It  may  be  very  cheaply  prepared  by  boiling 
together  for  an  hour  or  more,  in  a  small  quantity  of  water,  equal 
parts  of  flowers  of  sulphur  and  stone  lime.  A  convenient  quantity  is 
prepared  by  taking  5  pounds  of  sulphur  and  5  of  lime  and  boiling  in 
o  or  4  gallons  of  water  until  the  ingredients  combine,  forming  a 
brownish  liquid.    This  may  be  diluted  to  make  100  gallons  of  spraj^ 

Almost  any  of  the  insecticides  with  which  the  sulphur  may  be 
applied  will  kill  the  leaf  or  rust  mites,  but  the  advantage  of  the 
sulphur  arises  from  the  fact  that  it  forms  an  adhering  coating  on  the 
leaves  and  kills  the  young  mites  coming  from  the  eggs,  which  are 
very  resistant  to  the  action  of  insecticides. 

A  strongly  intrenched  popular  fallacy,  often  exposed  but  con- 
stantly being  revived,  is  that  sulphur  is  a  valuable  remedy  against 
insects  when  put  into  holes  bored  into  the  trunks  of  trees,  t'' .e  idea 
being  that  the  sulphur,  when  plugged  in,  is  carried  up  by  the  move- 
ment of  the  sap  into  the  branches  and  distributed  in  the  foliage, 
rendering  the  latter  distasteful  to  insects.  In  point  of  fact,  the 
sulphur  remains  exactly  where  it  is  placed,  and  is  of  no  possible 
advantage  from  an  insecticide  standpoint  or  any  other,  and  further- 
more the  treatment  is  mischievous  in  that  it  injures  to  that  extent 
the  soundness  of  the  trunk. 

PETROLEUM  OILS. 

The  emulsions  of  kerosene,  or  coal  oil,  with  soap  or  milk  have  long 
been  the  standard  insecticides  for  external  sucking  insects,  and  espe- 
cially the  aphides  and  scale  insects,  and  these  emulsions  still  are  the 
safest  and  most  reliable  means  of  getting  these  oils  upon  plants.  The 
use  of  kerosene  in  the  pure  state  as  an  insecticide  was  early  experi- 
mented with  by  Comstock  and  Hubbard,  and  the  feasibility  of  such 
applications  was  demonstrated,  but  the  greater  safety  in  the  use  of 
the  emulsions  resulted  in  a  discontinuance  of  the  use  of  the  pure  oils. 
Especially  during  the  last  twelve  years,  however,  the  use  of  these 
73159— Bui.  127—09 3 


18 

oils  in  the  pure  state  has  come  into  very  general  vogue,  more  particu- 
larly as  winter  washes  for  the  San  Jose  scale  and  allied  scale  insects, 
the  value  of  the  crude  oil  being  especially  demonstrated  by  Prof.  J.  B. 
Smith.  The  petroleum  oils  may  also  be  mechanically  combined  with 
water  by  means  of  especially  adapted  spray  pumps. 

In  addition  to  its  direct  application  to  plants,  kerosene  is  often  used 
as  a  means  of  destrojdng  insects  by  jarring  the  latter  from  plants  into 
pans  of  water  on  which  a  little  of  the  oil  is  floating,  or  by  jarring 
them  upon  cloths  or  screens  saturated  with  kerosene,  preferably  the 
crude  oil.  The  same  principle  is  illustrated  in  some  of  the  hopper- 
dozers,  or  machines  for  collecting  grasshoppers  and  leaf -hoppers. 

As  a  remedy  for  mosquitoes,  kerosene  has  proved  very  effective. 
It  is  employed  to  destroy  the  larvce  of  the  mosquitoes  in  their  favorite 
breeding  places  in  small  pools,  still  ponds,  or  stagnant  water;  and 
where  such  bodies  of  water  are  not  sources  of  drinking  supply  or  of 
value  for  their  fish,  especially  in  the  case  of  temporary  pools  from 
rains,  which  frequently  breed  very  disagreeable  local  swarms,  the  use 
of  oil  is  strongly  recommended.  The  kerosene  is  applied  at  the  rate 
of  1  ounce  to  15  square  feet  of  water  surface.  It  forms  a  uniform 
film  over  the  surface  and  destroys  all  forms  of  aquatic  insect  life, 
including  the  larvas  of  the  mosquito,  and  also  the  adult  females  coming 
to  the  water  to  deposit  their  eggs.  The  application  retains  its  effi- 
cienc}^  for  several  weeks,  even  with  the  occurrence  of  heavy  rains.  A 
light  grade  of  fuel  oil  is  preferred  for  this  purpose. 

The  methods  of  using  kerosene  in  the  pure  state  and  as  emulsions 
with  soa]3  and  milk  folloAv. 

Pure-kerosene  treatment. — This  consists  in  spraying  the  trees  with 
ordinary  illuminating  oil  (coal  oil  or  kerosene).  The  application  is 
made  at  any  time  during  the  winter,  preferably  in  the  latter  part,  and 
by  means  of  a  spray  pump  making  a  fine  mist  spray.  The  applica- 
tion should  be  made  with  the  greatest  care,  merely  enough  spray  being 
put  on  the  plant  to  moisten  the  trunk  and  branches  without  causing 
the  oil  to  flow  down  the  trunk  and  collect  about  the  base.  With  the 
use  of  this  substance  it  must  be  constantly  borne  in  mind  that  careless 
or  excessive  application  of  the  oil  will  be  very  apt  to  kill  the  treated 
plant.  The  application  should  be  made  on  a  bright,  dry  day,  so  that 
the  oil  will  evaporate  as  quickly  as  possible.  On  a  moist,  cloudy  day 
the  evaporation  is  slow,  and  injury  to  the  plant  is  more  apt  to  result. 
If  the  kerosene  treatment  be  adopted,  therefore,  it  must  be  with  a  full 
appreciation  of  the  fact  that  the  death  of  the  tree  may  follow.  This 
oil  has  been  used,  however,  a  great  many  times  and  very  extensively 
without  consequent  injury  of  any  kind.  On  the  other  hand,  its  care- 
less use  has  frequently  killed  valuable  trees.  Its  advantages  are  its 
effectiveness,  its  availability,  and  its  cheapness,  kerosene  spreading 

127 


19 

very  rapidly  and  much  less  of  it  being  required  to  wet  the  tree  than 
of  a  soap  and  water  spray.  Pure  kerosene  is  more  apt  to  be  injurious 
to  peach  and  plum  than  to  pear  and  apple  trees,  and  the  treatment  of 
the  former,  as  with  the  soap  wash,  should  be  deferred  until  spring, 
just  before  the  buds  swell.  With  young  trees  especially  it  is  well  to 
mound  up  about  the  trunk  a  few  inches  of  earth  to  catch  the  overflow 
of  oil,  removing  the  oil-soaked  earth  immediately  after  treatment. 

The  crude-petroleum  treatment. — Crude  petroleum  is  used  in  exactly 
the  same  way  as  is  the  common  illuminating  oil  referred  to  above. 
Its  advantages  over  kerosene  are  that,  as  it  contains  a  very  large  per- 
centage of  the  heavy  oils,  it  does  not  penetrate  the  bark  so  readily, 
and,  on  the  other  hand,  only  the  light  oils  evaporate,  leaving  a  coat- 
ing of  the  heavy  oils  on  the  bark,  which  remains  in  evidence  for 
months  and  prevents  any  young  scale,  which  may  come  from  the 
chance  individuals  not  reached  by  the  spray,  from  getting  a  foothold. 
Crude  i)etroleum  comes  in  a  great  many  different  forms,  depending 
upon  the  locality,  the  grade  successfully  experimented  with  in  the 
work  of  this  Bureau  showing  43°  Baume.  Crude  oil  showing  a  lower 
Baume  than  43°  is  unsafe,  and  more  than  45°  is  unnecessarily  high. 
The  lower  specific  gravity  indicated  (43°)  is  substantially  that  of  the 
refined  product,  the  removal  of  the  lighter  oils  in  refining  practically 
offsetting  the  removal  of  the  paraffin  and  vaseline.  The  same  cau- 
tions and  warnings  apply  to  the  crude  as  to  the  refined  oil. 

The  oil-water  treatment. — Various  pump  manufacturers  have  now 
placed  on  the  market  spraying  machines  which  mechanically  mix 
kerosene  or  crude  petroleum  with  water  in  the  act  of  spraying.  The 
attempt  is  made  to  regulate  the  proportion  of  kerosene  so  that  any 
desired  percentage  of  oil  can  be  thrown  out  with  the  water  and  be 
broken  up  by  the  nozzle  into  a  sort  of  emulsion.  Some  of  these  ma- 
chines, when  everything  is  in  good  working  order,  give  fairly  satis- 
factory results,  but  absolute  reliability  is  far  from  assured.  The 
best  outlook  for  good  apparatus  of  this  sort  seems  to  be  in  carrying 
the  oil  and  water  in  separate  lines  of  hose  to  the  nozzle,  uniting  them 
in  the  latter,  and  in  maintaining  an  absolute  equality  of  pressure  on 
both  the  oil  and  the  water  tanks  by  emplo3dng  compressed  air  as  the 
motive  force,  kept  up  by  an  air  pump,  the  air  chamber  communicat- 
ing with  both  of  the  liquid  receptacles.  One  or  more  manufacturers 
are  now  working  on  apparatus  of  this  general  description.  A  10-per- 
cent-strength  kerosene  can  be  used  for  a  summer  spray  on  trees  where 
the  San  Jose  scale  is  multiplying  rapidly  and  where  it  is  not  desirable 
to  let  it  go  unchecked  until  the  time  for  the  winter  treatment.  The 
winter  treatment  with  the  water-kerosene  sprays  may  be  made  at  a 
strength  of  20  per  cent  of  the  oil.  Applications  of  the  oil-water 
spray  should  be  attended  with  the  same  precautions  as  with  the  pure 

127 


20 

oil,  and  there  is  even  somewhat  greater  risk,  owing  to  the  natural 
tendency  one  has  to  apply  the  dilute  mixture  much  more  freely  than 
the  pure  oil  The  application  should  be  merely  enough  to  wet  the 
bark  and  the  mixture  should  not,  to  any  extent  at  least,  run  down 
the  trunk,  as  it  is  just  as  dangerous  to  the  tree  as  the  pure  oil. 

In  the  use  of  the  oil  sprays  noted  above,  one  who  has  not  had  expe- 
rience with  them  is  advised  to  make  some  careful  preliminary  tests 
to  fully  master  the  process,  preferably  waiting  two  or  three  weeks  to 
determine  the  results  before  entering  on  the  general  treatment  of  the 
orchard.  It  is  well,  also,  with  the  oil-water  mixtures  to  test  the  pump 
from  time  to  time,  spraying  into  a  glass  jar  or  bottle  to  determine  by 
actual  measurement  whether  the  correct  percentages  of  oil  and  water 
are  being  m.aintained. 

Kerosene  emulsion  (soap  formula) . — The  kerosene-soap  emulsion,  fol- 
lowing chiefl}'  the  Rilej-Hubbard  formula,  has  been  one  of  the  stand- 
ard means  against  scale  insects  for  twenty  years.  The  distillate 
emulsion  generally  employed  in  California  for  spraying  citrus  and 
other  trees  is  substantially  the  same  thing,  except  that  it  is  made  with 
the  California  distillate  or  petroleum  oil.  Crude  petroleum  of  any 
kind,  as  well  as  the  refined  product,  may  also  be  used  in  making  this 
emulsion.  The  use  of  the  soap  emulsions  against  the  San  Jcse  scale 
in  the  East  has  not  been  very  general,  on  account  of  the  greater  facil- 
ity with  which  the  pure  oil  or  oil-water  mixtures  can  be  applied. 
The  difficulty  of  obtaining  uniform  results  with  the  latter  has  led  to  a 
return  to  the  use  of  emulsions  to  some  extent,  and  there  can  be  no 
doubt  about  their  superior  merit  when  it  is  desired  to  dilute  the  pure 
oils.  Emulsions  may  be  applied  at  any  strength  with  absolute  con- 
fidence that  there  will  be  no  variation.  Where  the  emulsion  can  be 
prepared  wholesale  by  steam  power,  its  employment  is  attended  with 
no  difficulties.  In  California  it  is  prepared  by  oil  companies  and  sold 
at  very  slightly  more  than  the  cost  of  the  oil  and  soap  ingredients.  It 
is  made  after  the  following  formula : 

Petroleum gallons.^  2 

Wliale-oil  soap  (or  1  quart  soft  soap) pound —  i 

Water  (soft) Sallou__  1 

The  soap,  first  finely  divided,  is  dissolved  in  the  water  by  boiling 
and  immediately  added  boiling  hot,  away  from  the  fire,  to  the  oil. 
The  whole  mixture  is  then  agitated  violently  while  hot  by  being 
pumped  back  upon  itself  with  a  force  pump  and  direct-discharge 
nozzle  throwing  a  strong  stream,  preferably  one-eighth  inch  in  diam- 
eter. After  from  three  to  five  minutes'  pumping  the  emulsion  should 
be  perfect,  and  the  mixture  will  have  increased  from  one-third  to  one- 
half  in  bulk  and  assume  the  consistency  of  cream.  Well  made,  the 
emulsion  will  keep  indefinitely  and  should  be  diluted  only  as  wanted 
for  use. 

127 


In  limestone  regions,  or  where  the  water  is  very  hard,  some  of  the 
soap  will  combine  with  the  lime  or  magnesia  in  the  water,  and  more  or 
less  of  the  oil  will  be  freed,  especially  when  the  emulsion  is  diluted. 
Before  use,  such  water  should  be  broken  with  lye,  or  rain  water 
should  be  emplo3'^ed. 

Kerosene  emulsion  (milk  formula). — This  formula  is  as  follows: 

Kerosene gallons—  2 

Milk  (sour) gallon—  1 

Heating  is  unnecessary  in  making  the  milk  emulsion,  which  other- 
wise is  churned  as  in  the  former  case.  The  change  from  a  watery 
liquid  to  a  thick  buttery  consistency,  much  thicker  than  with  the  soap, 
takes  place  very  suddenly  after  three  to  five  minutes'  agitation.  With 
sweet  milk  difficulty  will  frequently  be  experienced,  and  if  the  emul- 
sion does  not  result  in  five  minutes,  the  addition  of  a  little  vinegar  will 
induce  prompt  action.  It  is  better  to  prepare  the  milk  emulsion  from 
time  to  time  for  immediate  use,  unless  it  can  be  stored  in  quantity  in 
air-tight  jars;  otherwise  it  will  ferment  and  spoil  after  a  week  or  two. 

The  distillate  emulsion. — This  wash  was  originated  by  Mr.  F.  Kahles, 
of  Santa  Barbara,  Cal.  It  has  been  recommended  by  the  California 
State  board  of  horticulture  and  has  found  very  general  use  in  the 
citrus  sections  of  the  State.  It  is  substantially  an  emulsion  of  crude 
petroleum,  made  in  the  same  way  as  the  kerosene  emulsion  described 
above,  except  that  a  greater  amount  of  soap  and  only  half  as  much  oil 
proportionately  is  used.  The  lessened  quantity  of  oil  enables  it  to  be 
made  comparatively  cheaply,  and  in  spite  of  this  reduction  in  the  oil, 
the  wash  is,  if  anything,  stronger  than  kerosene  emulsion,  judging 
from  the  experience  of  the  writer  with  both  these  washes  in  southern 
California. 

It  is  termed  distillate  spray,  because  the  oil  used  is  a  crude  distil- 
late of  the  heavy  California  petroleum.  The  product  used  for  pre- 
paring the  emulsion  should  have  a  gravity  of  about  28°  Baume,  and 
is  the  crude  oil  minus  the  lighter  oil,  or  what  distills  over  at  a  tem- 
perature between  250°  and  350°  C.  In  general  characteristics  it  is 
very  similar  to  lubricating  oil.  The  emulsion,  or,  as  it  is  generally 
known,  "  cream,"  is  prepared  as  follows:  Five  gallons  of  28°  gravity 
distillate;  5  gallons  of  water,  boiling;  1  to  1-1  pounds  of  whale-oil 
soap.  The  soap  is  dissolved  in  hot  water,  the  distillate  added,  and  the 
whole  thoroughly  emulsified  by  means  of  a  power  pump  until  a  rather 
heavy  yellowish,  creamy  emulsion  is  produced.  The  product  is  very 
similar  to,  but  rather  darker  in  color  than  the  ordinary  kerosene 
emulsion.  For  use  on  citrus  trees  it  is  diluted  with  from  12  to  15 
parts  of  water,  the  stronger  wash  for  the  lemon  and  the  weaker  for 
the  orange.  The  "  distillate  cream  "  is  commonly  prepared  and  sold 
by  oil  companies  or  individuals  at  from  10  to  12  cents  a  gallon, 

127 


22 

making  the  diluted  mixture  cost  in  the  neighborhood  of  a  cent  a 
gallon. 

The  distillate  spray  has  the  same  range  of  application  as  kerosene 
emulsion.  In  California  it  has  been  used  extensively  for  the  spray- 
ing of  citrus  trees,  and  when  so  used  has  been  often  charged  with 
injury  to  trees  and  especially  resulting  in  spotting  of  fruit.  If  this 
spray  be  applied  to  citrus  plants  in  spring  and  summer,  there  is 
danger  of  the  spotting  and  dropping  of  the  young  fruit  and  leaves. 
Where  several  applications  may  be  necessary  each  year,  gas  fumiga- 
tion is  undoubtedly  preferable.  Nevertheless  it  has  been  fully  demon- 
strated that  any  applications  made  to  citrus  trees  during  the  com- 
paratively dormant  season  in  October  and  November,  with  a  second 
treatment  if  necessary  in  January  and  February,  the  latter  just 
before  the  flower  spurs  start,  results  in  no  injury. 

How  to  use  the  emulsions. — During  the  growing  period  of  summer, 
for  most  aphides  and  other  soft-bodied  insects,  dilute  the  emulsion 
with  15  parts  of  water;  for  the  red  spider  and  other  plant-mites,  the 
same,  with  the  addition  of  1  ounce  of  floAvers  of  sulphur  to  the  gallon ; 
for  scale  insects,  the  larger  plant-bugs,  larva?,  and  beetles,  dilute  with 
from  7  to  10  parts  of  water.  Apply  with  spray  pump.  The  greatest 
dilution  noted  gives  4  per  cent  of  oil  and  the  lesser  dilutions  approxi- 
mately 6  and  8  per  cent. 

For  winter  applications  to  the  trunks  and  limbs  of  trees  in  the  dor- 
mant and  leafless  condition  to  destroy  scale  insects,  stronger  mixtures 
may  be  used,  even  to  the  pure  emulsion,  which  can  not  be  sprayed  suc- 
cessfully but  may  be  applied  with  brush  or  sponge.  Diluted  with  one 
or  more  parts  of  water  it  may  be  applied  in  spray  without  difficulty. 
The  use  of  the  pure  emulsion  is  heroic  treatment  and  only  advisable 
in  cases  of  excessive  infestation. 

The  winter  strengths  recommended  are  the  emulsion  diluted  with 
either  3,  4,  or  5  parts  of  water,  giving  approximately  17,  13,  and  11 
per  cent  of  oil.  These  dilutions  are  equivalent  in  strength  to  oil- 
water  sprays  containing  25,  20,  and  15  per  cent  of  oil,  because  rela- 
tively more  of  the  emulsion  is  held  by  the  bark.  The  two  stronger 
mixtures  may  be  used  on  the  apple  and  pear  and  the  weaker  one  on 
peach  and  plum. 

The  winter  treatment  may  be  followed  in  June  by  a  use  of  the  sum- 
mer wash  to  destroy  any  young  which  may  come  from  female  scales 
escaping  the  stronger  mixture. 

Cautions  regarding  use  of  oil  washes. — In  the  use  of  kerosene  washes, 
and,  in  fact,  of  all  oily  washes  on  plants,  the  application  should  be 
just  sufficient  to  wet  the  plant  without  allowing  the  liquid  to  run  down 
the  trunk  and  collect  about  the  root.  Usually,  in  the  case  of  young 
trees  at  least,  there  is  a  cavity  formed  by  the  swaying  of  the  tree  in 

127 


the  wind,  and  accumulation  of  the  insecticide  at  this  point,  unless 
precautions  be  taken,  may  result  in  the  death  or  injury  of  the  plant. 
Under  these  conditions  it  may  be  advisable  to  mound  up  the  trees 
before  spraying  and  firmly  pack  the  earth  about  the  bases.  Care 
should  be  taken  in  refilling  the  tank  that  no  free  oil  is  allowed  to 
accumulate  gradually  in  the  residue  left  at  the  bottom  when  spraying 
with  emulsions  or  oil-water  mixtures. 

Miscible  oils. — It  will  be  noted  that  the  difficulty  to  be  overcome  in 
the  use  of  oils  is  to  effect  their  dilution  to  render  them  harmless  to 
the  plant.  This  dilution  is  effected  with  great  accuracy  b}^  the  kero- 
sene-soap emulsions,  and  less  accurately  by  the  mechanical  emulsions 
of  oil  and  water.  There  have  appeared  during  the  last  few  years 
various  so-called  miscible  oils,  which  readily  and  permanently  mix 
with  water,  and  can  be  applied  with  the  same  readiness  and  accuracy 
of  strength  as  the  emulsion  of  kerosene  and  soap.  These  oils  have 
for  their  principal  ingredient  some  form  of  petroleum  rendered  solu- 
ble by  the  addition  of  a  percentage  of  vegetable  oils  and  cut  or  sapon- 
ified with  an  alkali,  and  they  are,  in  fact,  a  sort  of  liquid  petroleum 
soap.  They  are  sold  under  various  trade  names.  They  have  the 
disadvantage  of  costing  a  good  deal  more  than  the  standard  emul- 
sions or  the  lime-sulphur  wash  (see  p.  24),  but  have  the  great  advan- 
tage of  being  always  ready  for  immediate  use  without  troublesome 
preparation.  They  can  not  be  diluted  for  winter  applications  against 
scale  insects  with  more  than  10  or  15  parts  of  water  to  give  good  re- 
sults, and  there  is  some  danger  of  injury  to  the  trees  if  they  are  care- 
lessly or  excessively  applied.  They  have,  however,  a  very  useful  place, 
and  especially  as  furnishing  a  good  insecticide  where  only  a  few 
trees  are  to  be  treated  and  the  owner  would  probably  not  go  to  the 
trouble  of  preparing  an  emulsion  or  the  lime-sulphur  wash.  They 
have  been  so  far  principally  used  against  the  San  Jose  scale  as  dor- 
mant tree  washes. 

THE    RESIN    WASH. 

The  resin  wash  has  proved  of  greatest  value  in  California,  particu- 
larly against  the  red  scale  {Ghrysomphalus  aurantii  Mask.)  and  the 
black  scale  {Sais^etia  olecB  Bern.)  on  citrus  plants,  and  the  last  named 
and  the  San  Jose  scale  (Aspidiotus  perniciosus  Comst.)  on  deciduous 
plants,  and  will  be  of  use  in  all  similar  climates  where  the  occurrence 
of  comparatively  rainless  seasons  insures  the  continuance  of  the  wash 
on  the  trees  for  a  considerable  period,  and  where,  owing  to  the 
warmth,  the  multiplication  of  the  scale  insects  continues  almost  with- 
out interruption  throughout  the  year.  Wliere  rains  are  liable  to 
occur  at  short  intervals,  and  in  the  Northern  States,  the  quicker- 
acting  and  stronger  kerosene  washes  and  heavy  soap  applications  are 

127 


24 

preferable.     The  resin  wash  acts  by  contact,  having  a  certain  caustic 
effect,  but  i3rincipally  by  forming  an  impervious,  smothering  coating 
over  the  scale  insects.     The  application  may  be  more  liberal  than  with 
the  kerosene  washes,  the  object  being  to  wet  the  bark  thoroughly. 
The  wash  may  be  made  as  follows: 

Resin pounds.  _  20 

Crude  caustic  soda  (78  per  cent) do 5 

Fish   oil pints__  2i 

Water  to  make gallons 100 

Ordinary  commercial  resin  is  used,  and  the  caustic  soda  is  that  put 
up  for  soap  establishments,  in  large  200-pound  drums.  Smaller 
quantities  may  be  obtained  at  soap  factories,  or  the  granulated  caustic 
soda  (98  per  cent)  may  be  used — 3^  pounds  of  the  latter  being  the 
equivalent  of  5  pounds  of  the  crude.  Place  these  substances,  with 
the  oil,  in  a  kettle  with  water  to  cover  them  to  a  depth  of  3  or  4 
inches.  Boil  about  two  hours,  making  occasional  additions  of  water, 
or  until  the  compound  resembles  very  strong  black  coffee.  Dilute  to 
one-third  the  final  bulk  with  hot  water,  or  with  cold  w^ater  added 
slowly  over  the  fire,  making  a  stock  mixture,  to  be  diluted  to  the  full 
amount  as  used.  When  spraj^ed  the  mixture  should  be  perfectly 
fluid,  without  sediment,  and  should  any  appear  in  the  stock  mixture 
reheating  should  be  resorted  to ;  in  fact  the  wash  is  preferably  applied 
hot. 

As  a  winter  wash  for  scale  insects,  and  particularly  for  the  more 
resistant  San  Jose  scale  {Aspidiotus  perniciosus)  ^  stronger  washes  are 
necessary.  In  southern  California,  for  this  insect,  a  dilution  one- 
third  less,  or  water  to  make  6G|  gallons  instead  of  100  (see  for- 
mula), has  given  good  results.  In  Maryland,  with  this  insect,  it  has 
proved  necessary  to  use  the  wash  at  six  times  the  summer  strength 
to  destroy  all  of  the  well-protected  hibernating  scales;  and  with 
other  scale  insects  much  stronger  mixtures  than  those  used  in  Cali- 
fornia have  proved  ineffectual  in  the  East.  For  regions,  therefore, 
with  moderately  severe  winters  the  use  of  the  resin  wash  to  destroy 
hibernating  scale  insects  seems  inadvisable. 

THE   LIME-SULPHUR  WASH. 

In  California,  where  the  San  Jose  scale  first  appeared,  the  standard 
remedy  for  it  is  the  lime-sulphur-salt  wash,  a  mixture  formerly  used 
as  a  sheep  dip  in  Australia  and  employed  with  little  change  against 
the  San  Jose  scale.  This  wash  was  naturally  first  thought  of  on  the 
discovery  of  the  San  Jose  scale  in  eastern  orchards.  The  earlier  tests, 
however,  conducted  by  this  office  in  1894,  gave  unfavorable  results, 
and  the  experimentation  which  followed  resulted  in  the  demonstra- 
tion of  several  distinct  and  valuable  methods  of  control  noted  below. 

127 


25 

Later  studies  of  the  action  of  this  wash  in  California  led  the  writer 
in  1900  to  give  it  a  further  careful  trial  in  the  East,  with  most  suc- 
cessful results,  demonstrating  that,  with  favoring  conditions,  i.  e., 
absence  of  dashing  rains  for  a  few  days  after  the  application,  it  would 
give  just  as  good  results  in  the  Eastern  States  as  on  the  Pacific  coast. 
A  year  later  (1901-2)  very  elaborate  tests  conducted  by  Doctor 
Forbes  in  Illinois  showed  that  fairly  hard  rains  will  not  alwa37s  in- 
validate spraying  with  this  mixture.  A  vast  amount  of  experience 
of  the  most  practical  kind  since  gained,  contributed  to  by  all  the 
eastern  experiment  stations  and  by  the  big  commercial  fruit  growers 
of  the  Middle  and  Eastern  States,  has  fully  demonstrated  the  prac- 
tical merit  of  this  wash  and  its  superiority  to  others  in  point  of  safety 
to  trees  and  in  cheapness.  Its  disadvantages  are  the  difficulty  of 
preparation  and  the  heavy  wear  whicn  it  entails  on  apparatus — objec- 
tions, however,  which  do  not  offset  its  notable  advantages,  particu- 
larly for  commercial  orchard  work  or  where  the  number  of  trees  to 
be  treated  is  sufficient  to  warrant  the  trouble  of  its  preparation.  It 
is,  in  fact,  the  standard  spray  now  used  in  commercial  orchards  for 
the  San  Jose  scale. 

Composition  and  preparation. — In  the  matter  of  composition  of  the 
wash,  scarcely  any  two  experimenters  agree.  Salt  was  a  part  of  the 
original  composition  of  the  sheep  clip  and  has  long  been  retained, 
with  the  idea  that  it  added,  perhaps,  to  the  caustic  qualities,  and  par- 
ticularly to  the  adhesiveness  of  the  wash.  For  the  latter  purpose  a 
very  small  amount  only,  1  or  2  pounds  to  the  bushel  of  lime,  need  be 
added,  following  the  custom  in  the  preparation  of  whitewash  mix- 
tures. In  practical  exj^erience,  however,  the  salt  seems  to  have  been 
of  very  little  benefit  and  is  therefore  omitted  in  the  formula  now 
given.  The  proportion  of  lime  and  sulphur  is  a  matter  of  some  in- 
difference. The  mixture  obtained  is  sulphide  of  lime,  and  if  an  ex- 
cess of  lime  is  used  it  simply  remains  undissolved  in  the  mixture  and 
adds  to  the  whitewashing  character  of  the  application.  Too  much 
lime  is  distinctly  objectionable,  however,  because  of  the  greater  diffi- 
culty of  spraying  and  harder  wear  on  the  pump  and  nozzles.  The 
formula  here  given  is  substantially  the  one  which  has  been  hitherto 
recommended  by  this  Bureau,  reduced  to  the  45  or  50  gallon  basis,  or 
the  capacity  of  the  ordinary  kerosene  barrel  commonly  used  in  its 
preparation  by  the  steam  method. 

Unslaked    lime _' pounds__  20 

Flowers  of  sulphur do 15 

Water  to  make gallous__  45  to  50 

The  flowers  of  sulphur,  although  requiring  somewhat  longer  cook- 
ing, seems  to  make  a  better  wash  than  ground  sulphur,  but  the  latter 
may  be  employed.     Stone  lim^e  of  good  quality  should  be  secured  and 

127 


26 

slaked  in  a  small  quantity  of  water,  say  one-third  the  full  dilution. 
The  sulphur,  previously  mixed  up  into  a  stiff  paste,  should  be  added 
at  once  to  the  slaking  lime.  The  whole  mixture  should  be  boiled  for 
at  least  one  hour,  either  in  an  iron  kettle  over  a  fire  out  of  doors  or  in 
barrels  by  steam.  Prolonged  boiling  increases  the  percentage  of  the 
higher  sulphides,  but  the  practical  end  is  obtained  by  boiling  for  the 
time  indicated.  In  the  process  of  making,  the  color  changes  from 
yellow  to  the  clear  brown  of  sulphide  of  lime,  except  for  the  excess 
of  lime  floating  in  it.  After  an  hour's  boiling  the  full  quantity  of  cold 
water  can  be  added,  and  the  mixture  should  then  be  promptly  applied 
in  order  to  get  its  full  strength  before  the  higher  sulphides  are  lost 
by  cooling  and  crystallizing  out.  In  transferring  to  the  spray  tank 
it  should  be  passed  through  an  iron  screen  or  strainer,  and  the  tank 
itself  should  be  provided  with  an  effective  agitator. 

Directions  for  use. — The  wash  is  a  winter  application  and  can  not 
be  applied  to  trees  in  leaf.  It  may  be  applied  at  any  time  after  the 
falling  of  foliage  in  early  winter  and  prior  to  the  swelling  of  the  buds 
in  spring.  The  later  the  application  can  be  made  the  better  the  re- 
sults, and  the  best  j^eriod  is  just  before  the  buds  swell  in  March  or 
April.  It  will  probably  be  necessary  also  to  make  this  application 
every  year,  or  at  least  as  often  as  the  San  Jose  scale  develops  in  any 
numbers.  The  wash  kills  the  San  Jose  scale  not  only  by  direct  caustic 
action,  but  also  by  leaving  a  limy  coating  on  the  trees,  which  remains 
in  evidence  until  midsummer  or  later  and  kills  or  prevents  the  settling 
of  young  scale  insects  which  may  come  from  parents  escaping  the 
winter  action. 

The  wear  on  pumps  and  nozzles  can  be  kept  to  a  minimum  by  care- 
fully washing  the  apparatus  promptly  after  use.  The  Vennorel 
nozzle  is  the  best  one  for  the  wash,  and  additional  caps  may  be  se- 
cured to  replace  worn  ones.  The  use  of  an  air  or  other  gas  pressure 
pump  instead  of  the  ordinary  liquid  pump  will  save  the  wear  of  the 
lime  on  the  pump.  In  spraying  with  this  wash  clothing  is  ruined, 
and  only  the  oldest  garments  should  be  worn.  Care  should  be  taken 
also  to  protect  the  eyes  to  avoid  unnecessary  inflammation. 

Range  of  usefulness. — Tliis  wash  is  distinctively  the  remedy  for  the 
San  Jose  scale  and  is  particularly  effective  in  applications  to  the 
smooth-barked  fruit  trees — such  as  peach,  pear,  and  f)lum.  In  the 
case  of  the  apple  the  terminal  twigs  are  often  covered  with  a  fuzzy 
growth,  more  pronounced  in  some  varieties  than  others,  which  pre- 
vents the  wash  from  properly  coating  the  bark.  The  young  from 
scale  insects  which  escape  destruction  at  such  points,  for  the  reason 
indicated  or  from  imperfect  spraying,  are  driven  out  onto  the  new 
growth,  or,  in  the  case  of  fruit  spurs,  onto  the  fruit,  so  that  a  tree  on 
which  the  scale  has  been  pretty  thoroughly  exterminated  may  never- 

127 


27 

theless  present  badly  spotted  fruit.*  In  such  cases  the  additional 
use  of  some  one  of  the  oil  sprays  may  be  necessary. 

This  wash  is  of  equal  value  against  closely  allied  scale  pests,  such 
as  Forbes's  scale  and  the  West  Indian  peach  scale,  and  late  sprayings 
are  quite  effective  against  the  scurfy  scale  and  the  oyster-shell  scale. 

The  spring  application,  just  before  the  buds  swell,  has  been  demon- 
strated by  Prof.  J.  M.  Aldrich  to  kill  most  of  the  eggs  of  the  apple 
aphis,  and  Mr.  Fred  Johnson,  of  this  Bureau,  has  found  that  it  is 
equally  effective  in  destroying  the  eggs  of  the  pear-tree  Psylla.  It 
is  useful  against  other  pests  which  hibernate  about  the  leaf  buds  of 
fruit  trees,  as,  for  example,  the  pear-leaf  blister-mite  and  the  silvery 
mite  of  the  peach,  and  in  California  Mr.  Clark  has  shown  that  it  is 
an  entirely  satisfactory  remedy  for  the  peach  twig  borer  {Anarsia 
lineatella  Zell.). 

In  addition  to  this  range  of  usefulness  against  insect  pests  this 
wash  has  shown  itself  to  be  a  valuable  fungicide,  notably  for  the 
peach  leaf  curl,  sprayed  trees  being  practically  immune  from  this 
disease,  so  that  the  cost  of  treatment  in  the  case  of  the  peach  is  often 
more  than  made  good  by  the  fungicidal  benefit  alone.  Later  experi- 
ence indicates  its  usefulness  also  as  a  winter  application  for  apple 
scab  and  possibly  for  other  plant  diseases. 

TIME  TO  SPSAY  FOR  STICKING  INSECTS. 

For  the  larger  plant-bugs  and  the  aphides,  or  active  plant-lice,  and 
all  other  sucking  insects  which  are  present  on  the  plants  injuriously 
for  comparatively  brief  periods,  or  at  most  during  summer  only,  the 
treatment  should  be  immediate,  and  if  in  the  form  of  spray  on  the 
plants,  at  a  strength  which  will  not  injure  growing  vegetation. 

For  scale  insects  and  some  others,  as  the  pear  Psylla,  which  hiber- 
nate on  the  plants,  two  or  more  strengths  are  advised  with  most  of 
the  liquid  insecticides  recommended,  the  weaker  for  summer  applica- 
ti>c«is  and  the  more  concentrated  as  winter  washes.  The  summer 
washes  for  scale  insects  are  most  effective  against  the  young,  and 
treatment  sliould  begin  with  the  first  appearance  of  the  larvae  in  the 
spring  or  any  of  the  later  broods,  and  should  be  followed  at  intervals 
of  seven  days  with  two  or  three  additional  applications.  The  first 
brood,  for  the  majority  of  species  in  temperate  regions,  will  appear 
during  the  first  three  weeks  in  May.  Examination  from  time  to 
time  with  a  hand  lens  will  enable  one  to  determine  when  the  young 
of  any  brood  appear. 

The  winter  washes  may  be  used  whenever  summer  treatment  can 
not  be  successfully  carried  out,  and  are  particularly  advantageous  in 
the  case  of  deciduous  plants  with  dense  foliage  which  renders  a  thor- 

°  See  Bui.  46,  Bur.  Eut.,  p.  54. 
127 


28 


ough  wetting  difficult  in  summer,  or  with  scale  insects  which  are  so 
irregular  in  the  time  of  disclosing  their  young  that  many  summer 
treatments  would  be  necessary  to  secure  anywhere  near  complete  ex- 
termination. In  the  winter  also,  with  deciduous  trees,  very  much  less 
liquid  is  required,  and  the  spraying  may  be  much  more  expeditiously 
and  thoroughly  done.  In  the  case  of  badly  infested  trees,  a  vigorous 
pruning  is  advisable  as  a  preliminary  to  treatment. 

DUSTING  AND  SPRAYING  APPARATUS. 

POWDER  DISTRIBUTEBS. 

For  the  application  of  powders  the  dusting  bags  already  described 
(pp.  11-12)  are  very  satisfactory  for  field  work.  Much  more  expen- 
sive and  more  rapid 
machine  distributers 
have  been  devised,  but 
these  are  rarely  used. 
For  garden  work 
some  of  the  small 
powder  bellows  and 
blowers  are  excellent. 
These  cost  from  $2 
to  $8. 


LIQUID  SPBAYEES. 

For  the  application 
of  poisons  in  liquid 
form  the  prime  essen- 
tial is  an  apparatus 
which  will  break  up 
the  liquid  into  a  fine 
mist-like  spray  that 
will  coat  every  leaf 
and  every  other  part 
of  the  plant  as  lightly  as  is  compatible  with  thoroughness.  The 
essential  features  of  such  an  apparatus  are  the  force  pump,  suitable 
hose,  and  nozzles  or  spray  tips.  The  leading  pump  manufacturers 
now  put  out  a  large  variety  of  spraying  apparatus  suited  for  all 
ordinary  needs,  including  the  small  knapsack  pumps,  barrel  and  tank 
pumps,  and  geared  and  power  sprayers.  For  limited  indoor  opera- 
tions a  hand  atomizer  or  even  a  sprinkling  can  with  fine  rose  tip 
may  be  made  to  do  fair  service. 

127 


Fig.  3. — Barrel  spray  pump.     (From  Waite.) 


29 

The  barrel  pump. — This  is  the  commonest  form  of  spraying  appara- 
tus, and  is  supplied  in  many  different  styles;  or,  a  suitable  spray 
pump  can  be  combined  with  an  empty  50-gallon  kerosene  barrel  "with- 
out much  difficulty.  (See  fig.  3.)  This  apparatus  may  be  hauled 
about  on  a  sled  or  in  a  -wagon  or  a  two-wheeled  cart. 

Tank  outfits. — For  larger  operations  it  is  much  better  to  have 
a  specially  constructed  rectangular  or  half-round  spray  tank  of  a 
caj^acit}^  of  200  or  300  gallons.  Such  an  apparatus  enables  an  ele- 
vated platform  to  be  mounted  on  the  wagon  and  tank,  greatly  facili- 
tating spraying  of  the  higher  parts  of  trees,  as  indicated  in  the 
accompanying  illustration  (fig.  4).  The  ideal  sprayer  for  extensive 
work  combines  such  a  tank,  with  platform,  with  gasoline  or  steam 
power  spray  pump. 


Fig.  4. — Power  sprayer  at  work  iu  apple  orchard.     (From  Scott  and  Quaintance.) 

Geared  sprayers. — For  low -growing  regidarly  planted  crops  it  is 
sometimes  possible  to  use  spraying  apparatus  which  gets  its  power 
by  means  of  a  sprocket  wheel  from  the  axle  of  the  Avagon.  Several 
types  of  spraying  apparatus  of  this  kind  are  on  the  market,  suited 
especially  for  the  treating  of  crops  like  potatoes  and  strawberries, 
and  the  .spraying  of  vineyards.  In  orchards  it  is  not  often  possible  to 
have  the  wagon  constantly  in  motion,  and  geared  sprayers  are  not  as  a 

rule  available. 

Gas-pressure  sprayers. — Some  very  successful  spraying  machnies 
have  been  made  which  have  as  their  motive  power  gas  pressure.  This 
pressure  m.ay  be  derived  from  compressed  air  or  carbonic  acid  gas 
cylinders.     It  is  an  ideal  way  of  applying  liquid  sprays,  and  has  a 

127 


30 

special  applicability  to  oil-^Yater  mixtures  (see  p.  19).     Ultimately 
this  principle  may  come  into  much  more  general  use. 

Hose,  nozzle,  and  agitator. — The  hose  and  nozzle  are  two  very  essen- 
tial elements  of  a  good  spraying  apparatus.  The  verj'  best  three- 
eighths,  one-fourth,  or  one-half  inch  3-ply  or  4-ply  hose  should  be 
bought.  A  cheap  or  inferior  hose  will  not  stand  the  pressure  and 
heavy  wear  of  spraying.  For  orchard  spraying  a  length  of  25  feet 
is  the  least  that  should  be  used,  and  better  35  feet,  and  longer  with 
large  apparatus  where  it  may  be  possible  to  spray  more  than  one  row 
at  a  time.  Several  lines  of  hose  may  be  operated  with  a  strong  spray 
pump.  Each  line  of  hose  should  be  supplied  with  an  extension  rod  8 
or  10  feet  long.  This  rod  may  be  an  ordinary  bamboo  pole  into  which 
a  small  brass  tube  is  fitted  carrying  the  nozzle,  or  the  hose  may 
terminate  in  a  small  gas  pipe — a  rather  heavy  device  and  useful  for 
short  length  only. 

Of  the  many  types  of  nozzles  which  have  been  devised,  the  best 
is  that  known  as  the  Vermorel  (fig.  5).  Where  the  power  is  suffi- 
cient, a  double  or  even  quadruple  nozzle  may  be  at- 
tached to  each  line  of  hose.  Most  of  the  nozzles  on 
the  market  are  inferior,  and  this  special  type  should 
be  insisted  upon. 

A  very  necessary  feature  of  spray  tanks  is  a  device 

for  keej)ing  the  liquid  constantly  agitated  to  keep  up 

.    a  uniform  mixture  or  prevent  the  settling  of  the  poi- 

spray     nozzle,    son  or  solid  constituents  of  the  wash.     This  may  be 

(From  waite.)      accomplished   by    constant    stirring   with   a    paddle. 

Most  of  the  spraying  apparatus  now  on  the  market  are  provided 

with  automatic  agitators. 

SELECTION    OF    SPRAYING    OUTFIT. 

P'or  limited  garden  work  or  for  the  treatment  of  low  plants  a 
simple  bucket  pump  can  be  used,  which  will  cost  about  $6,  or  the 
knapsack  pump,  costing  about  $14. 

For  home  orchards  of  small  size  a  barrel  pump  with  one  line  of 
hose  will  serve  every  purpose,  the  complete  outfit  costing  $12  to  $18. 

For  larger  operations,  with  two  lines  of  hose  and  nozzles,  a  barrel 
outfit,  costing  from  $25  to  $30,  may  be  used. 

Tank  outfits,  v>'ith  double  cylinder  pumps  suitable  for  an  orchard 
of  a  thousand  bearing  trees,  may  be  obtained  at  a  cost  of  from  $75 
to  $90. 

The  power  sprayers  are  much  more  expensive,  costing  $200  to  $300 

or  more. 

127 


31 


DIRECTIONS    FOR    SPRAYING. 


Thorough  work  in  spraying  must  be  done,  or  failure  will  result. 
To  accomplish  this,  power  sufficient  to  break  up  the  liquid  into  a  fine 
mist  is  essential.  This  makes  it  possible  for  the  tree  to  be  thoroughly 
and  thinly  wetted  with  the  spray  without  waste,  and  the  ideal  appli- 
cation is  to  accomplish  this  without  causing  the  liquid  to  collect  in 
drops  and  fall  from  the  tree.  More  of  the  spray  is  left  on  the  leaves 
with  a  light  spray  than  with  a  heavy  application,  which  causes  the 
globules  to  coalesce  and  a  shower  of  drops  to  fall  to  the  ground.  To 
get  a  proper  spray,  it  should  be  possible  to  produce  a  pressure  of  at 
least  75  pounds,  or,  with  power  outfits,  of  125  to  150  pounds. 

Fruit  trees  of  average  size  or,  if  apple,  such  as  would  produce 
10  or  15  bushels  of  fruit,  will  require  from  3  to  7  gallons  of  spray 
to  wet  them  thoroughly.  For  smaller  trees,  such  as  plum  and  cherry, 
1  gallon  to  the  tree  may  be  sufficient.  In  spraying  orchard  trees 
and  other  fruit  trees  it  will  often  be  found  convenient,  especially  with 
a  smaller  apparatus,  to  spray  on  each  side  half  of  each  tree  in  a 
row  at  a  time,  and  finish  on  the  return. 

A  light  rain  will  remove  comparatively  little  of  the  poison,  but 
a  dashing  rain  may  necessitate  a  renewal  of  the  application. 

HYDROCYANIC-ACID  GAS  TREATMENT. 

The  use  of  hydrocyanic-acid  gas  originated  in  southern  California 
in  work  against  citrus  scale  insects,  and  was  perfected  by  a  long 
period  of  experimentation  by  an  agent  of  this  Bureau,  Mr.  D.  W. 
Coquillett.  It  is  undoubtedly  the  most  thorough  method  known  of 
destroying  scale  insects  and  especially  is  it  the  best  treatment  for 
citrus  trees,  the  abundance  of  foliage  and  nature  of  growth  of 
which  render  thorough  spraying  difficult,  but,  on  the  other  hand, 
enable  the  comparatively  heayj'-  tents  employed  in  fumigation  to  be 
thrown  or  drawn  over  the  trees  rapidl}''  without  danger  of  breaking 
the  limbs.  One  good  gassing  is  usually  the  equivalent  of  two  or 
three  sprayings,  the  gas  penetrating  to  every  particle  of  the  surface 
of  the  tree  and  often  effecting  an  almost  complete  extermination, 
rendering  another  treatment  unnecessary  for  two  years  or  more. 
(See  fig.  G.) 

The  gas  treatment  is  just  as  effective  against  scale  insects  on  decidu- 
ous orchard  fruit  trees,  as  has  been  demonstrated  by  a  good  deal  of 
work  done  in  the  East,  notably  in  Maryland  by  Professor  Johnson ; 
but  the  difficulty  and  expense  of  the  treatment  as  compared  with  the 
value  of  the  crop  protected  makes  it  as  a  rule  prohibitive  in  the  case 
of  deciduous  fruits.  This  does  not  apply,  however,  to  nursery  stock, 
which  may  be  brought  together  compactly  and  treated  in  mass  in 

127 


32 

fumigating  rooms  or  houses.  The  general  spread  of  the  San  Jose 
scale  in  the  East  has  made  such  fumigation  of  nursery  stock,  even 
^Yhen  infestation  is  not  shown  or  suspected,  a  necessary  procedure 
before  shipment  or  sale,  to  give  the  utmost  assurance  of  safety  to  thp 
purchaser.  Similarly  this  gas  is  the  principal  agency  employed  in 
disinfecting  plant  material  coming  from  abroad,  and  will  be  the  chief 
agency  for  such  work  wherever  quarantine  regulations  prevail. 

Another  very  important  use  for  hydrocyanic-acid  gas  is  as  a  means 
of  controlling  insect  pests  in  greenhouses  and  cold  frames.  The 
process  is  a  special  one,  however,  and  entails  considerable  variation, 
owing  to  the  wide  range  of  plants  to  be  considered.  The  details  of 
the  process  are  given  in  a  special  publication  of  the  Bureau  of  Ento- 
mology (Circular  No.  37),  which  will  be  supplied  to  anyone  inter- 
ested. 


Fig.  6. — Tenting  trees  for  gas  treatment,  San  Diego,  Cal.     (Author's  illustration.) 

A  more  recent  use  for  this  gas  is  in  disinfecting  houses  of  insect 
pests  and  vermin.  The  details  of  this  treatment  are  given  in  Circular 
46,  revised  edition,  of  the  Bureau  of  Entomology. 

In  all  work  with  hydrocyanic-acid  gas,  its  extremely  poisonous  pm- 
ture  must  he  constantly  kept  in  mind  and  the  greatest  precautior.s 
must  he  taken  to  avoid  inhaling  it. 


FUMIGATION   OF   NURSERY   STOCK. 

For  the  fumigation  of  nursery  stock  or  imported  plant  material 
in  a  dormant  or  semidormant  condition,  a  building  or  room  should 
be  provided,  which  can  be  closed  practically  air-tight,  and  it  should  be 
fitted  with  means  of  ventilation  above  and  at  the  side,  operated  from 
without,  so  that  the  poisonous  gas  can  be  allowed  to  escape  without 

127 


the  necessity  of  anyone  entering  the  chamber.  The  gas  is  generated 
by  combining  potassium  cyanide,  sulpliuric  acid,  and  water.  The 
proportions  of  the  chemicals  are  as  follows :  Refined  potassium  cyan- 
ide (98  per  cent),  1  ounce;  commercial  sulphuric  acid,  1  ounce;  water, 
3  fluid  ounces  to  ever}'  hundred  cubic  feet  of  space  in  the  fumigating 
room.  For  comparatively  green  or  tender  material  the  same  amounts 
may  be  used  to  150  cubic  feet  of  space. 

The  generator  of  the  gas  may  be  any  glazed  earthenware  vessel  of 
1  or  2  gallons  capacity  and  should  be  placed  on  the  floor  of  the  fumi- 
gating room,  and  the  water  and  acid  necessary  to  generate  the  gas 
added  to  it  in  the  order  named.  The  cyanide  should  be  added  last, 
preferably  in  lumps  the  size  of  a  walnut,  and  the  premises  promptly 
vacated  and  the  door  made  fast.  Treatment  should  continue  forty 
minutes. 

ORCHARD   FUMIGATION. 

The  methods  of  fumigating  citrus  stock  in  California  are  now 
(1908)  being  given  a  thorough  investigation  by  this  Bureau.  As 
already  noted,  the  gas  process  has  been  a  leading  method  in  Cali- 
fornia for  more  than  twenty  years,  but  the  results,  while  normally 
good,  have  not  always  been  satisfactory.  The  object  of  the  investiga- 
tion now  under  way  is  to  thoroughly  standardize  the  process ;  in  other 
words,  (1)  to  determine  the  proper  strength  to  be  used  for  the  differ- 
ent scale  pests  under  different  climatic  conditions,  and  also  under  the 
different  seasonal  conditions  of  the  tree;  (2)  to  determine  the  phj'si- 
ological  effect,  if  any,  on  the  tree  and  fruit;  and  (3)  to  perfect  the 
mechanical  means  of  handling  tents  and  generating  the  gas,  and  de- 
termine the  proper  quantity  and  quality  of  chemicals  to  use.  The 
results  of  this  investigation  will  be  the  basis  of  a  special  report  on  gas 
fumigation,  and  will  probably  modify  somewhat  the  directions  given 
below,  which  are  reproduced  from  the  previous  edition  of  this  bulletin. 

The  fumigation  for  the  white  fly  in  Florida  is  a  special  problem 
and  has  been  under  investigation  by  this  Bureau  for  two  years.  The 
results  of  this  investigation,  including  general  directions  for  fumiga- 
tion, will  be  given  in  Bulletin  No.  76. 

Amounts  of  chemicals  to  use. — The  amounts  of  chemicals  used  var}'' 
with  the  size  of  the  tree  and,  as  now  employed  in  California,  are  con- 
siderably in  excess  of  the  amounts  recommended  as  recently  as  1898. 
The  gas  treatment  was  first  chiefly  used  against  the  black  scale  and  at 
a  season  of  the  jea.r  when  these  scales  were  all  in  a  young  stage  and 
easily  killed.  The  effort  is  now  made  not  only  to  kill  the  black 
scale,  but  also  the  red  and  purple  scales,  and  to  do  more  effective 
work  than  formerly  against  tlie  black  scale.  The  amounts  of  chem- 
icals ordinarily  advised  and  commonly  employed  in  Los  Angeles, 

127 


34 

Orange,  and  some  other  counties  in  southern  California  are  indicated 
in  the  subjoined  table,  published  by  the  horticultural  commissioners 
of  Riverside  County,  Cal. 

Table  1.— Amounts  of  chemicals  and  water  ordinarily  used  for  trees  of  different 

sises. 


Height 
of  tree. 

Diameter 
of  tree. 

Water. 

Cyanide, 
0.  P.,  98 

per  cent. 

Sulphuric 

acid,  66  per 

cent. 

Feet. 

Feet. 

Ounces. 

Ounces. 

Ounces. 

6 

4 

2 

1 

1 

8 

6 

3 

n 

11 

19 

8 

5 

2J 

2J 

12 

14 

11 

SJ 

16 

16 

17 

8 

9 

20 

16-20 

22 

10 

12 

20-24 

18-23 

30 

14 

16 

24-30 

20-28 

34 

18 

18 

30-36 

25-30 

52 

24 

■      28 

The  proportions  here  recommended  are  thoroughly  effective  for  the 
black  scale  at  the  proper  season,  and  measurably  effective  also  for  the 
California  red  scale  and  the  purple  scale.  AMiere  the  treatment  is 
designed  to  be  one  of  extermination  for  these  latter  scale  pests, 
from  one-third  to  one-half  more  of  cyanide  and  acid  is  employed,  as 
indicated  by  the  subjoined  table,  furnished  by  Mr.  G.  Havens,  of 
Riverside.  The  amounts  here  recommended  may  be  employed  also 
for  compact  trees  with  dense  foliage  or  in  moist  coast  regions  where 
stronger  doses  are  needed. 

Table  2. — Excessive  amounts  of  chemicals  used  for  absolute  extermination  oj 

scale  insects.^ 


Height 
of  tree. 

Diameter 
through 
foliage. 

Water. 

Sulphuric 
acid. 

Cyanide. 

Time  to 

leave  tent 

on  tree. 

Feet. 

Feet. 

Fluid  ozs. 

Fluid  ozs. 

Ounces. 

Minutes. 

6 

3-  4 

3 

n 

3-1 

20 

8 

!>-  6 

6 

2i 

2 

30 

10 

7-10 

15 

5-  6 

4  -  5 

35-40 

12 

9-12 

20-  30 

7-  9 

5J-  7J 

40 

14 

12-14 

30-  35 

9-12 

8  -10 

40 

16 

12-15 

a5-  40 

12-14 

10  -12 

40 

13 

14-16 

45-  55 

15-18 

12  -15 

40  r)0 

20 

16-18 

60-  70 

20-22 

16  -20 

45-50 

23 

16-18 

70-  75 

22-25 

20 

50 

24 

18-20 

75-  80 

25-30 

22  -26 

50 

27 

20-24 

8.5-100 

30-36 

28  -32 

CO 

30 

20-28 

100-110 

30-44 

32  -38 

60 

<*A  fumigation  of  the  orangery  of  the  Department,  December  3,  1900,  demonstrated  that 
0.15  of  a  gram  of  cyanide  to  the  cubic  foot,  or  a  little  more  than  half  an  ounce  to  the 
hundred  cubic  feet,  is  completely  exterminatiye  of  scale  insects,  effectually  killing  the 
eggs,  even  of  the  black,  purple,  and  other  scales.  The  strength  mentioned  is  that 
ordinarily  recommended  for  violet  houses,  and  the  results  are  scarcely  comparable  to 
the  proportions  recommended  in  Tables  1  and  2,  for  the  reason  that  in  these  tables  the 
amount  of  cyanide  Is  greatly  lessened  with  larger  trees,  and,  furthermore,  that  the 
orangery  probably  retained  the  gas  more  effectually  than  would  be  the  case  with  cloth 
tents.  Nevertheless,  it  is  interesting  to  know  that  a  comparatively  inconsiderable 
strength  of  cyanide,  when  applied  under  the  best  conditions,  will  prove  thoroughly 
effective  against  the  eggs  as  well  as  the  insects  in  all  stages. 
127 


35 

The  duration  of  the  treatment  indicated  in  the  second  table  varies 
with  the  size  of  the  tree,  but  in  general  at  least  forty  minutes  should 
be  allowed. 

In  Florida  fumigation  for  the  white  fly  can  be  successfully  prac-' 
ticed  only  during  the  short  period  in  winter  when  the  insect  does 
not  occur  in  the  winged  stage.  This  period  covers  from  two  and  a 
half  to  three  months,  namely,  December,  January,  and  February,' 
varying  with  the  climatic  conditions  of  different  years.  This  is  the 
dry  season  for  Florida,  and  the  trees  are  in  a  dormant  condition, 
with  the  leafage  well  matured  and  hardened,  and  it  is  possible  to 
api)ly  a  greater  strength  than  Avould  be  safe  under  California  condi- 
tions. The  strength  recommended  is  approximately  the  same  as  for 
deciduous  nursery  stock,  viz,  1  ounce  of  cj'anide  to  100-115  cubic  feet 
of  space,  with  a  duration  of  40  minutes. 

General  directions. — In  the  fumigation  of  growing  stock,  citrus  or 
other,  the  treatment  consists  in  inclosing  the  tree  with  a  tent  and 
filling  the  latter  with  poisonous  fumes  generated  in  the  same  way  as 
described  for  nursery  stock  except  that  less  of  the  chemicals  is  used. 
The  treatment  is  made  at  night  for  trees  in  foliage,  which  includes 
all  work  in  citrus  orchards,  to  avoid  the  much  greater  likelihood  of 
injury  to  tender  foliage  in  the  sunlight.  The  vessels  for  setting  off 
the  charges  of  cyanide  and  acid  may  be,  for  small  doses,  any  ordinary 
earthenware  jars.  For  large  trees  requiring  heavy  doses,  tall  wooden 
pails  have  proved  more  satisfactory,  two  generators  being  employed 
for  the  very  largest  trees. 

It  is  important  that  the  water  he  put  in  the  vessel  first,  then  the 
acid,  and  lastly  the  cyanide.  If  the  water  and  cj'anide  are  f)ut  in 
the  vessel  first  and  the  acid  poured  in  afterwards,  there  is  danger  of  an 
explosion  which  Avill  scatter  the  acid  and  burn  the  tents  and  the  oper- 
ator. In  the  spring,  when  the  trees  are  tender  with  new  growth,  and 
in  early  fall  when  the  oranges  are  nearly  grown  and  the  skins  are 
likely  to  be  easily  marred,  and  also  with  young  trees,  it  is  advisable 
to  add  one-third  more  water  than  ordinarily  used,  or  to  add  the 
cyanide  in  larger  lumps.  This  causes  the  gas  to  generate  more  slowly 
and  with  less  heat,  and,  if  the  tents  are  left  over  the  trees  a  third 
longer,  the  effectiveness  of  the  treatment  will  not  be  lessened.  The 
person  handling  the  chemicals  should  always  have  an  attl^ndant  with 
a  lantern,  to  hold  up  the  tent  and  enable  the  cyanide  to  be  quickly 
dropped  into  the  generator,  and  to  facilitate  the  prompt  exit  of  the 
operator. 

Trees  are  fumigated  for  the  black  scale  in  southern  California  in 
October,  or  preferably  in  November.  The  red  and  other  scales  may 
be  treated  with  gas  at  any  time,  but  preferably  at  the  season  already 
indicated.     In  California  most  of  the  work  is  done  by  contract,  or 

127 


36 


('under  the  direct  supervision  of  the  county  horticultural  commission- 
ers, in  some  cases  the  tents  and  material  being  furnished  at  a  merely 
nominal  charge,  together  with  one  experienced  man  to  superintend 
the  work,  while  a  crew  of  four  men  oi:)erate  the  tents,  the  wages  of  the 
director  and  men  being  paid  by  the  owner  of  the  trees. 

Construction  and  handling  of  tents. — The  tents  now  employed  are  of 

two  kinds,  the  "  sheet "  tent 
of  octagonal  shape  for  large 
trees,  and  the  "  ring  *'  tent 
for  trees  under  12  feet  in 
height.  The  ring  tents,  or, 
as  they  are  also  called,  the 
bell  tents,  are  bell  -  shaped 
and  have  a  hoop  of  half-inch 
gas  pipe  fastened  within  a 
foot  or  so  of  the  opening. 
Two  men  can  easily  throw 
one  of  these  tents  over  a 
small  tree.  An  equipment  of 
3G  or  40  ring  tents  can  be 
handled  by  four  men.  They 
are  rapidly  thrown  over  the 
trees  by  the  crew,  and  the 
director  follows  closely  and 
introduces  the  chemicals.  By 
the  time  the  last  tent  has 
been  adjusted  the  first  one 
can  be  removed  and  taken 
across  to  the  adjoining  row. 
An  experienced  crew,  with 
one  director,  can  treat  350  to 
400  5-year-old  trees,  averag- 
ing 10  feet  in  height,  in  a 
single  night  of  eleven  or 
twelve  hours.  The  cost  un- 
der such  conditions  averages 
about  8  cents  a  tree. 

With  large  trees  the  large 
sheet  tents  are  drawn  over  them  by  means  of  uprights  and  pulley 
blocks.  Two  of  these  sheets  are  necessary  for  very  large  trees,  the 
first  being  drawn  halfway  over  and  the  second  drawn  up  and  made 
to  overlap  the  first.  In  the  case  of  trees  from  24  to  30  years  old  and 
averaging  30  feet  in  height,  about  50  can  be  treated  in  a  night  of  ten 
or  twelve  hours  Avith  an  equipment  of  12  or  15  tents,  the  cost  being 

127 


Fig.  7. — Method  of  hoisting 
(After   Craw.) 


sheet  tent. 


37 

about  75  cents  per  tree.  It  is  not  practicable  to  treat  trees  above  30 
feet  in  height. 

The  handling  of  the  bell  tents  is  simple  and  needs  no  further  de- 
scription, but  the  large  tents  are  not  so  easily  operated,  and  the 
method  of  adjusting  the  great  flat  octagonal  sheets  over  the  trees, 
while  simple  enough  when  once  understood,  warrants  a  description. 
The  machinery  employed  consists  of  two  simple  uprights,  with  at- 
tached blocks  and  tackle  (fig.  7).  The  uprights  are  about  25  feet 
high,  of  strong  Oregon  pine,  2  by  4  inches,  and  are  provided  at  the 
bottom  with  a  braced  crossbar  to  give  them  strength  and  to  prevent 
their  falling  to  either  side  while  the  tent  is  being  raised.  A  guy 
rope  is  attached  to  the  top  of  each  pole  and  held  to  steady  it  by  a  mem- 
ber of  the  crev*'  stationed  at  the  rear  of  the  tree.  The  tent  is  hoisted 
by  means  of  two  ropes  70  feet  long,  which  pass  through  blocks,  one 
fixed  at  the  top  of  the  pole  and  the  other  free.  The  tent  is  caught 
near  the  edge  b}'  taking  a  hitch  around  some  solid  object,  such  as  a 
green  orange,  about  which  the  cloth  is  gathered.  By  this  means  the 
tent  may  be  caught  anywhere  without  the  trouble  of  reversing  and 
turning  the  heavy  canvas  to  get  at  rings  or  other  fastenings  attached 
at  particular  points.  The  two  remaining  members  of  the  operating 
crew  draw  the  tent  up  against  and  over  one  side  of  the  tree  by  means 
of  the  pulley  ropes  sufficiently  to  cover  the  other  side  of  the  tree  when 
the  tent  falls.  The  poles  and  tent  together  are  then  allowed  to  fall 
forward,  leaving  the  tent  in  position.  Sufficient  skill  is  soon  acquired 
to  carry  out  rapidly  the  details  of  this  operation,  so  that  little  time 
is  lost  in  transferring  the  tents  from  tree  to  tree,  even  when  the  trees 
approximate  the  limit  in  height.  A  single  pair  of  hoisting  poles 
answers  for  all  the  tents  used. 

Some  of  the  tents  employed  are  of  great  size,  one  described  by  Mr. 
Havens  having  a  diameter  of  7G  feet.  It  is  constructed  of  a  central 
j^iece  50  feet  square,  of  10-ounce  army  duck.  Four  triangular  side 
pieces  or  flaps  of  8-ounce  duck,  10  feet  wide  in  the  middle,  are  strongly 
sewed  to  each  side  of  the  central  sheet,  forming  an  octagonal  sheet  70 
feet  in  diameter.  About  the  whole  sheet  is  then  sewed  a  strip  of 
G-ounce  duck,  1  yard  wide.  The  tent  is  handled  by  means  of  ropes 
and  pulleys.  A  l-|-inch  manila  rope  is  sewed  about  the  border  of  the 
central  piece  in  an  octagonal  pattern.  Rings  are  attached  to  this  rope 
at  each  of  the  eight  corners  thus  formed,  and  also  on  either  side  of 
the  tent.  To  these  rings  the  pulley  ropes  are  fastened,  and  the  tent 
is  elevated  over  the  trees  and  handled  very  much  as  indicated  in  fig  7. 

The  canvas  for  the  tents,  blue  or  brown  drilling  or  8  to  10  ounce 
duck,  may  be  rendered  comparatively  impervious  to  the  gas  by 
painting  lightly  with  boiled  linseed  oil.  This  has  the  objection,  how- 
ever, of  stiffening  the  fabric  and  adding  considerably  to  its  weight; 
it  also  frequently  leads  to  its  burning  by  spontaneous  combustion 
unless  carefully  watched  until  the  oil  is  dry.    A  much  better  material 

127 


38 

than  oil  is  found  in  a  product  obtained  from  the  leaves  of  the  common 
prickly  pear  cactus  {Opuntia  engelmanni)  ,y}\\\ch.  grows  in  abundance 
in  the  Southwest.  The  liquor  is  obtained  by  soaking  chopped-iip 
leaves  in  water  for  twenty- four  hours.  It  is  given  body  and  color  by 
the  addition  of  glue  and  yellow  ocher  or  Venetian  red,  and  is  applied 
to  both  sides  of  the  canvas  and  rubbed  well  into  the  fiber  of  the  cloth 
with  a  brush. 

Some  practical  experience  is  necessary  to  fumigate  successfully, 
and  it  will  therefore  rarely  be  wise  for  anyone  to  undertake  it  on  a 
large  scale  without  having  made  preliminary  experiments. 

BISULPHID  OF  CAEBON  VAPOR. 

In  line  with  the  use  of  hydrocyanic-acid  gas  is  the  employment  of 
the  vapor  of  bisulphid  of  carbon  to  destroy  insects  on  low-growing 
plants,  such  as  the  aphides  on  melon  and  squash  vines.  The  treat- 
ment, as  successfully  practiced  by  Professors  Garman  and  Smith, 
consists  in  covering  the  young  vines  with  small  tight  boxes  12  to  18 
inches  in  diameter,  of  either  wood  or  paper,  and  introducing  under 
each  box  a  saucer  containing  one  or  two  teaspoonfuls  (1  or  2  drams) 
of  the  very  volatile  liquid  bisulphid  of  carbon.  The  vines  of  older 
I^lants  may  be  wrapped  about  the  hill  and  gathered  in  under  larger 
boxes  or  tubs,  and  a  greater,  but  proportional,  amount  of  the  liquid 
used.  The  covering  should  be  left  over  the  plants  from  three-quarters 
of  an  hour  to  an  hour,  and  with  50  to  100  boxes  a  field  may  be  treated 
with  comparative  rapidity. 

Bisulphid  of  carbon  has  proved  also  to  be  the  most  effective  means 
of  disinfecting  grape  cuttings  suspected  of  being  infested  with 
phylloxera."  The  cuttings  arc  inclosed  in  a  tight  barrel  or  fumi- 
gating box,  and  the  bisulphid  of  carbon,  poured  out  in  a  shallow  dish, 
is  put  on  top  of  the  cuttings.  An  ordinary  saucerful  of  the  chemical 
is  enough  for  a  box  3  feet  cube.  The  treatment  lasts  from  forty-five 
to  ninety  minutes.  This  is  a  pretty  strong  fumigation,  but  the  dor- 
mant condition  of  the  cuttings  makes  this  possible. 

REMEDIES  FOR  SUBTERRANEAN  INSECTS. 

Almost  entire  dependence  is  placed  on  the  caustic  washes,  or  those 
that  act  externall}^,  for  insects  living  beneath  the  soil  on  the  roots  of 
plants,  including  both  sucking  and  biting  insects,  prominent  among 
which  are  the  white  grubs,  maggots  in  roots  of  cabbage,  radishes, 
onions,  etc.,  cutworms,  wireworms,  apple  and  peach  root-aphides,  the 
grape  phylloxera,  and  many  others. 

The  insecticide  must  be  one  that  will  go  into  solution  and  be  carried 
down  by  water.     Of  this  sort  are  the  kerosene  emulsions  and  resin 

cBul.  192,  Cal.  Agr.  Ezp.  Sta.,  1907. 


39 

wash — the  former  preferable — the  potash  fertilizers,  muriate  and 
kaiiiit,  and  bisulphid  of  carbon.  The  simple  remedies  are  applica- 
tions of  strong  soap  or  tobacco  washes  to  the  soil  about  the  crown; 
or  soot,  ashes,  or. tobacco  dust  buried  about  the  roots;  also  similarly 
employed  are  lime  and  gas  lime.  Submersion,  wherever  the  practice 
of  irrigation  or  the  natural  conditions  make  it  feasible,  has  proved  of 
the  greatest  service  against  the  phylloxera. 

HOT  WATER. 

As  a  means  of  destroying  root-aphides,  and  particularly  the  woolly 
aphis  of  the  apple,  the  most  generally  recommended  measure  hitherto 
is  the  use  of  hot  water,  and  this,  while  being  both  simple  and  inex- 
pensive, is  thoroughly  effective,  as  has  been  demonstrated  by  practical 
experience.  Water  at  nearly  the  boiling  point  may  be  applied  about 
the  base  of  young  trees  without  the  slightest  danger  of  injury  to  the 
trees,  and  should  be  used  in  sufficient  quantity  to  wet  the  soil  thor- 
oughly to  a  depth  of  several  inches,  as  the  aphides  may  penetrate 
nearly  a  foot  below  the  surface.  To  facilitate  the  wetting  of  the 
roots  and  the  extermination  of  the  aphides,  as  much  of  the  surface 
soil  as  possible  should  be  first  removed. 

By  a  hot-water  bath  slightly  infested  stock  can  be  easily  freed  of 
the  aphides  at  the  time  of  its  removal  from  the  nurserj'^  rows.  The 
soil  should  be  dislodged  and  the  roots  pruned,  and  in  batches  of  a 
dozen  or  so  the  roots  and  lower  portion  of  the  trunks  should  be  im- 
mCTsed  for  a  few  seconds  in  water  kept  at  a  temperature  of  130°  to 
150°  F.  A  strong  soap  solution  similarh'  heated  or  a  fifteen  times 
diluted  kerosene  emulsion  will  give  somewhat  greater  penetration  and 
be  more  effective,  although  the  water  alone  at  the  temperature  named 
should  destroy  the  aphides. 

Badly  infested  nursery  stock  should  be  destroyed,  since  it  would  be 
worth  little  even  with  the  aphides  removed. 

TOBACCO  DUST. 

Some  very  successful  experiments  conducted  by  Prof.  J.  M.  Sted- 
man  demonstrated  the  very  satisfactory  protective,  as  well  as  reme- 
dial value  of  finely  ground  tobacco  dust  against  the  woolly  aphis. 
The  desirability  of  excluding  the  aphis  altogether  from  nursery  stock 
is  at  once  apparent,  and  this  Professor  Stedman  shoAvs  to  be  possible 
by  placing  tobacco  dust  freely  in  the  trenches  in  which  the  seedlings 
or  grafts  are  planted  and  in  the  orchard  excavations  for  young  trees. 
Nursery  stock  may  be  continuously  protected  by  laying  each  spring  a 
line  of  the  dust  in  a  small  furrow  on  either  side  of  the  row  and  as 
close  as  possible  to  the  tree,  and  covering  loosely  with  earth.  For 
large  trees,  both  for  protection  and  the  destruction  of  existing 
aphides,  from  2  to  5  pounds  of  the  dust  should  be  distributed  from 
the  base  outward  to  a  distance  of  2  feet,  first  removing  the  surface 

127 


40 

soil  to  a  depth  of  from  4  to  6  inches.  The  tobacco  kills  the  aphides 
by  leaching  through  the  soil,  and  acts  for  a  j^ear  or  so  as  a  bar  to 
reinfestation.  The  dust  is  a  waste  product  of  tobacco  factories,  costs 
about  1  cent  per  pound,  and  possesses  the  additional  value  of  being 
worth  fully  its  cost  as  a  fertilizer. 

Since  its  early  recommendation  marked  success  has  been  reported 
from  the  use  of  tobacco  dust.  A  notable  instance  is  that  given  by 
Mr.  M.  B.  Waite,  of  the  Bureau  of  Plant  Industry,  who  applied  a 
ton  of  tobacco  waste,  costing  $25,  in  his  orchard,  with  the  result  of 
entirely  renewing  the  vigor  of  his  trees  and  producing  a  strong 
stubby  growth  of  twigs.  A  peck  of  tobacco  dust  was  placed  about 
each  of  his  larger  trees  in  a  circle  of  2  or  3  feet  around  the  trunk, 
and  a  slightlv  smaller  amount  about  trees  from  one  to  three  years 
old. 

KEROSENE  EMULSION  AND  RESIN  V/ASH. 

Either  the  kerosene-and-soap  emulsion  or  the  resin  wash,  the 
former  diluted  fifteen  times  and  the  latter  at  the  strength  of  the 
winter  mixture,  are  used  to  saturate  the  soil  about  the  affected  plants 
and  either  left  to  be  carried  down  by  the  action  of  rains  or  washed 
down  to  greater  depths  by  subsequent  waterings. 

For  the  grape  phylloxera  or  the  root-aphis  of  the  peach  or  apple, 
make  excavations  2  or  3  feet  in  diameter  and  6  inches  deep  about  the 
base  of  the  plant  and  pour  in  5  gallons  of  the  wash.  If  not  a  rainy 
season,  a  few  hours  later  wash  down  with  5  gallons  of  water  and 
repeat  with  a  like  amount  the  day  following.  It  is  better,  however, 
to  make  this  treatment  in  the  spring,  when  the  more  frequent  rains 
will  take  the  place  of  the  waterings. 

For  root-maggots  enough  of  the  wash  is  put  at  the  base  of  the 
plant  to  wet  the  soil  to  a  depth  of  1  to  2  inches,  preferably  followed 
after  an  hour  with  a  like  amount  of  water. 

For  white  grubs  in  strawberry  beds  or  in  lawns  the  surface  should 
be  wetted  with  kerosene  emulsion  to  a  depth  of  2  or  3  inches,  follow- 
ing with  copious  waterings  to  be  repeated  for  two  or  three  days.  The 
larva;  go  to  deeper  and  deeper  levels  and  eventually  die. 

POTASH  FERTILIZERS. 

For  white  grubs,  wireworms,  cutworms,  corn  root-worms,  and  like 
insects,  on  the  authority  of  Prof.  J.  B.  Smith,  either  kainit  or  the 
muriate  of  potash — the  former  being  the  better — are  broadcasted  in 
fertilizing  quantities,  preferably  before  or  during  a  rain,  so  that  the 
material  is  dissolved  and  carried  into  the  soil  at  once.  These  not 
only  act  to  destroy  the  larva  in  the  soil,  but  are  deterrents,  and  truck 
lands  constantly  fertilized  with  these  substances  are  noticeably  free 
from  attacks  of  insects.  This,  in  a  measure,  results  from  the  in- 
creased vigor  and  greater  resisting  power  of  the  plants,  which  of  itself 

127 


41 

more  than  compensates  for  the  cost  of  the  treatment.  The  value  of 
these  fertilizers  against  the  wireworms  is,  however,  questioned  by- 
Prof.  J.  H.  Comstock. 

For  the  root-aphis  of  peach  and  apple,  work  the  fertilizer  into  the 
general  surface  of  the  soil  ftbout  the  trees,  or  put  it  into  a  trench 
about  the  tree  2  feet  distant  from  the  trunk. 

For  cabbage  and  onion  maggots,  apply  in  little  trenches  along  the 
rows  at  the  rate  of  300  to  500  pounds  to  the  acre,  and  cover  with  soil. 

These  fertilizers  (and  the  nitrate  of  soda  is  nearly  as  good)  are  also 
destructive  to  the  various  insects  which  enter  the  soil  for  hibernation 
or  to  undergo  transformation. 

BISULPHID  OF   CARBON". 

This  is  the  great  French  remedy  for  the  phylloxera,  150,000  acres 
being  now  subjected  to  treatment  with  it,  and  applies  equally  well  to 
all  other  root-inhabiting  aphides.  The  treatment  is  made  at  any 
season  except  the  period  of  ripening  of  the  fruit  and  consists  in  mak-' 
ing  holes  about  the  vines  1  foot  to  16  inches  deep  and  pouring  into 
each  about  one-half  ounce  of  the  bisulphid,  and  closing  the  holes  with 
the  foot.  The  injections  are  made  about  1|  feet  apart,  and  not  closer 
to  the  vines  than  1  foot.  It  is  better  to  use  a  large  number  of  small 
doses  than  a  few  large  ones.  Hand  injectors  and  injecting  plows  are 
emjDloyed  in  France  to  put  the  bisulphid  into  the  soil  about  the  vines, 
but  a  short  stick  or  iron  bar  may  take  the  place  of  these  injectors 
for  limited  tracts.  i 

The  use  of  bisulphid  of  carbon  for  the  woolly  aphis  is  the  same  as 
for  the  grape  root-aphis  or  phylloxera.  It  should  be  applied  in  two 
or  three  holes  about  the  tree  to  a  depth  of  from  6  to  12  inches  and  not 
closer  than  1^  feet  to  the  tree.  An  ounce  of  the  chemical  should  bo 
introduced  into  each  hole,  which  should  be  immediately  closed. 

For  root -maggots  a  teaspoonful  is  poured  into  a  hole  near  the  base 
of  the  plant,  being  covered  as  above. 

For  ant  nests  an  ounce  of  the  substance  is  poured  into  each  of  sev- 
eral holes  made  in  the  space  occupied  by  the  ants,  the  openings  being 
then  closed;  or  the  action  is  made  more  rapid  by  covering  with  a 
wet  blanket  for  ten  minutes  and  then  exploding  the  vapor  at  the 
mouth  of  the  holes  with  a  torch,  the  explosion  driving  the  fumes 
more  thoroughly  through  the  soil. 

SUBMERSION". 

This  very  successful  means  against  the  phylloxera  is  now  practiced 
over  some  75,000  acres  of  vineyards  in  France  which  were  once  de- 
stroyed by  the  grape  root-aphis,  and  the  production  and  quality  of 
fruit  has  been  fully  restored.  In  this  country  it  will  be  particularly 
available  in  California  and  in  all  arid  districts  where  irrigation  is 

127 


42 

practiced;  otherwise  it  will  be  too  expensive  to  be  profitable.  The 
best  results  are  secured  in  soils  in  which  the  water  will  penetrate 
rather  slowly,  or  from  6  to  18  inches  in  twenty-four  hours;  in  loose, 
sandy  soils  it  is  impracticable  on  account  of  the  great  amount  of 
water  required.  Submersion  consists  in  keeping  the  soil  of  the  vine- 
yard flooded  for  from  eight  to  twenty  days  after  the  fruit  has  been 
gathered  and  active  growth  of  the  vine  has  ceased,  or  during  Sep- 
tember or  October,  but  while  the  phylloxera  are  still  in  active  devel- 
opment. Early  in  September  eight  to  ten  days  will  suffice ;  in  October 
fifteen  to  twenty  days,  and  during  the  winter,  forty  to  sixty  days. 
Supplementing  the  short  fall  submergence  a  liberal  July  irrigation, 
amounting  to  a  forty-eight  hour  flooding,  is  customary  to  reach  any 
individuals  surviving  the  fall  treatment,  and  which  in  midsummer 
are  very  susceptible  to  the  action  of  water. 

To  facilitate  the  operation,  vineyards  are  commonly  divided  by 

embankments  of  earth  into  square  or  rectangular  plats,  the  former  for 

♦level  and  the  latter  for  sloping  gi'ound,  the  retaining  walls  being 

protected  by  coverings  of  reed  grass,  etc.,  during  the  first  year,  or 

imtil  they  may  be  seeded  to  some  forage  plant. 

This  treatment  will  destroy  many  other  root-attacking  insects  and 
tliose  hibernating  beneath  the  soil,  and,  in  fact,  is  a  very  ancient  prac- 
tice in  certain  oriental  countries  bordering  the  Black  Sea  and  the 
Grecian  Archipelago. 

REMEDIES  FOR  INSECTS  AFFECTING  GRAIN  AND  OTHER  STORED 

PRODUCTS. 

GENERAL  METHODS  OF  TREATMENT. 

The  chief  loss  from  insects  of  this  class  is  to  grains  in  farmers'  bins, 
or  grain  or  grain  products  in  stores,  mills,  and  elevators,  although 
in  the  warmer  latitudes  much  injury  results  from  infestation  in  the 
field  between  the  ripening  of  the  grain  and  its  storage  in  bins  or 
granaries.  Fortunately,  the  several  important  grain  insects  arc 
amena])le  to  like  treatment.  Aside  from  various  important  pre- 
ventive operations,  such  as,  in  the  South,  prompt  thrashing  of  grain 
after  harvesting,  the  thorough  cleansing  of  bins  before  refilling, 
removal  of  waste  harboring  insects  from  all  parts  of  granaries  and 
mills,  and  care  to  prevent  the  introduction  of  "  woeviled  "  grain, 
there  are  four  valuable  remedial  measures,  viz,  agitation  of  tho 
grain,  heating,  dosing  with  bisulphid  of  carbon,  and  fumigating  with 
sulphur  dioxid. 

The  value  of  agitating  or  handling  grain  is  well  known,  and  when- 
ever, as  in  elevators,  grain  can  be  transferred  or  poured  from  one  bin 
into  another,  grain  pests  are  not  likely  to  trouble.  The  benefit  Avill 
depend  uj)on  the  frequency  and  thoroughness  of  the  agitation.     In 

127 


43 

France  machines  for  shaking  the  grain  violently  have  been  used  with 
success.  Winnowing  weeviled  grain  is  also  an  excellent  preliminary- 
treatment.  ' 
Eaising  the  temperature  of  the  grain  in  closed  retorts  or  revolving 
cylinders  to  130°  to  150°  F.  will  kill  the  inclosed  insects  if  continued 
for  three  to  five  hours,  but  is  apt  to  injure  the  germ,  and  is  not  ad- 
vised in  case  of  seed  stock.  The  simplest  and  most  effective  remedies 
are  the  use  of  either  bisulphid  of  carbon  or  sulphur  dioxid. 

BISULPHID   OF   CARBON." 

Character  and  method  of  application. — This  is  a  colorless  liquid  with 
very  offensive  odor,  which,  however,  passes  off  completely  in  a  short 
time.  It  readily  volatilizes,  and  the  vapor,  which  is  very  deadly  to 
insect  life,  is  heavier  than  air  and  settles  and  fills  any  compartment 
or  bin  in  the  top  of  which  the  liquid  is  placed.  It  may  be  distributed 
in  shallow  dishes  or  tins  or  in  saturated  waste  on  the  top  of  grain  in 
bins,  and  the  gas  will  settle  and  permeate  throughout  the  mass  of 
the  grain.  In  large  bins,  to  hasten  and  equalize  the  operation,  it  is 
well  to  put  a  quantity  of  the  bisulphid  in  the  center  of  the  grain  by 
thrusting  in  balls  of  cotton  or  waste  tied  to  a  stick  and  saturated  with 
the  liquid,  or  by  means  of  a  gas  pipe  loosely  plugged  at  one  end,  down 
which  the  liquid  may  be  poured  and  the  plug  then  loosened  with  a 
rod.  Prof.  H.  E.  Weed  reports  that  in  Mississippi  the  chemical  is 
commonly  poured  directly  onto  the  grain.  In  moderately  tight  bins 
no  further  precaution  than  to  close  them  well  need  be  taken,  but  in 
open  bins  it  will  be  necessary  to  cover  them  over  with  a  blanket  to 
prevent  the  too  rapid  dissipation  of  the  vapor.  The  bins  or  buildings 
should  be  kept  closed  from  twenty-four  to  thirty-six  hours,  after 
which  a  thorough  airing  should  be  given  them. 

Limited  quantities  at  a  time  may  often  be  advantageously  subjected 
to  treatment  in  small  bins  before  being  j^laced  for  long  storage  in 
large  masses,  and  especially  whenever  there  is  danger  of  introducing 
infested  grain. 

The  bisulphid  is  applied  at  the  rate  of  1  pound  to  the  ton  of  grain, 
or  a  pound  to  a  cubic  space  10  feet  on  a  side. 

In  the  case  of  mills,  elevators,  or  larger  granaries  the  application 
may  be  best  made  on  Saturday  night,  leaving  the  building  closed  over 
Sunday,  with  a  watchman  without  to  see  that  no  one  enters  and  to 
guard  against  fire.  The  bisulphid  should  be  first  distributed  in  the 
upper  story,  working  downward  as  rapidly  as  possible  to  avoid  the 
settling  vapor,  using  the  substance  very  freely  in  waste  or  dishes  at 
all  points  of  infestation  and  over  bins  throughout  the  building.  If 
the  building  be  provided  with  an  exterior  means  of  descent  (such  as 

°  See  Farmers'  Bulletin  No,  145,  Carbou  Bisulphid  as  au  Insecticide. 
127 


44 

a  fire  escape)  it  would  be  preferable  to  begin  with  the  lower  story  and 
work  upAvard. 

This  insecticide  may  also  be  used  in  other  stored  products,  as  peas, 
beans,  etc.,  and  very  satisfactorily  where  the  infested  material  can  be 
inclosed  in  a  tight  can,  chest,  or  closet  for  treatment.  It  may  also  be 
emploA'^ed  to  renovate  and  protect  wool  or  similar  material  stored  in 
bulk.  " 

The  bisulphid  costs,  in  oO-pound  cans,  10  cents  per  pound,  and  in 
small  quantities,  of  druggists,  25  to  35  cents  per  pound. 

Caution. — The  bisulphid  may  be  more  freely  employed  with  milling 
grain  than  with  that  intended  for  seeding,  since,  when  used  excess- 
ively, it  may  injure  the  germ.  It  must  always  be  remembered  that 
the  vapor  is  highly  inflammable  and  explosive,  and  that  no  fire  or 
lighted  cigars,  etc.,  should  be  in  the  building  during  its  use.  If  ob- 
tained in  large  quantities  it  should  be  kept  in  tightly  closed  vessels 
and  away  from  fire,  preferably  in  a  small  outbuilding. 

A^Hiile  this  gas  is  not  especiaih'-  dangerous  to  human  beings,  care 

should  be  taken  to  avoid  unnecessary  inhalation.     It  has  a  slight 

suffocating  effect,  and  if  inhaled  for  some  time  produces  dizziness, 

which  should  be  a  Avarning  to  the  operator  that  it  is  time  to  seek  fresh, 

pure  air. 

SULPHUR  DIOXID. 

The  fumes  of  burning  sulphur,  namely,  sulphur  dioxid,  with  some 
sulj)hur  trioxid,  have  long  been  one  of  the  standard  insecticide  gases 
for  the  destruction  of  insect  pests  in  rooms  or  dwellings,  and  notably 
for  the  bedbug  {Cimex  Icctularius  L.).  Doctor  Stiles,  of  the  Public 
Health  and  Marine-Hospital  Service,  reports  very  successful  fumiga- 
tion  and  disinfection  of  frame  cottages  at  a  seaside  resort  for  bedbug 
infestation  by  burning  sulphur  at  the  rate  of  2  pounds  of  stick  sulphur 
for  each  1,000  cubic  feet  of  space.  Sulphur  candles  for  such  fumiga- 
tion are  a  standard  supply  material  to  be  purchased  anywhere.  Sul- 
phur fumes  are  also  emploj^ed  for  disinfection  from  disease  germs, 
and  also  in  the  more  recent  yellow-fever  work  for  the  destruction  of 
mosquitoes  in  dwellings.  The  chief  objection  to  the  sulphur  fumiga- 
tion arises  from  the  strong  bleaching  action  of  the  fumes  in  the  pres- 
ence of  moisture  and  their  powerful  destructive  action  on  vegetation. 
!  For  the  disinfection  of  ships  and  ships'  cargoes,  particularly  of 
grain,  sulphur  dioxid,  under  the  name  of  "  Clayton  gas,"  is  now  being 
extensively  employed.  To  determine  its  efficiency  and  its  effect  on 
the  grains  treated,  a  considerable  series  of  experiments  was  conducted 
by  the  Bureau."  These  experiments  showed  that  svdphur  dioxid, 
under  pressure  such  as  can  be  maintained  in  an  air-tight  compartment 
or  in  the  hold  of  a  ship,  has  great  penetrating  power  and  is  very  effi- 
cient as  a  means  of  destroying  all  kinds  of  insects.     The  germinating 

«  Bui.  60,  Bur.  Ent.,  U.  S.  Dept.  Agric,  pp.  139-153.     1906. 
127 


45 

power  of  seeds  is  quickly  destroyed,  but  no  injury  results  to  the  feed- 
ing or  cooking  quality  of  cereals.  It  can  not  be  employed  in  the  case 
of  living  plants,  nor  with  moist  fruits  or  products,  such  as  apples  or 
bananas.  The  best  results  in  the  case  of  insects  infesting  grains  and 
seeds,  such  as  Calandra  and  Bruchus,  Avhich  are  often  inclosed  in  the 
seeds,  were  obtained  by  the  use  of  a  low  percentage  (1  to  5  per  cent  of 
gas)  for  a  period  of  twelve  to  twenty- four  hours.  Employed  in  this 
way  the  gas  is  a  very  effective  means  of  disinfecting  stored  grain  or 
similar  products  not  intended  for  planting,  and  has  the  additional 
advantage  of  entirely  eliminating  the  danger  of  explosion  and  fire. 

GENERAL  CONSIDERATIONS  ON  THE  CONTROL  OF  INSECTS. 
ADVANTAGE    OF   PROMPT   TREATMENT. 

The  importance  of  promptness  in  the  treatment  of  plants  attacked 
by  insects  can  not  be  too  strongly  insisted  upon.  The  remedy  often 
becomes  useless  if  long  deferred,  the  injury  having  already  been  ac- 
complished or  gone  beyond  repair.  If,  by  careful  inspection  of 
plants  from  time  to  time,  the  injury  can  be  detected  at  the  very  outset, 
treatment  is  comparatively  easy  and  the  result  much  more  satisfac- 
tory. Preventive  work,  therefore,  should  be  depended  on  as  much  as 
possible,  rather  than  remedial  treatment  later;  the  effort  being  to 
forestall  any  serious  injury  rather  than  to  patch  up  damage  which 
neglect  has  allowed  to  become  considerable. 

KILLING  INSECTS  AS  A  PROFESSION. 

It  may  often  liappen  that  the  amount  of  work  in  a  community  is 
sufficient  to  induce  one  or  more  persons  to  undertake  the  treatment 
of  plants  at  a  given  charge  per  tree  or  per  gallon  of  the  insecticide 
employed.  Where  this  is  the  case,  and  the  contracting  parties  are 
evidently  experienced  and  capable,  it  is  frequently  more  economical  in 
the  end  to  emplo}'^  such  experienced  persons,  especially  when  a  guar- 
antee is  given,  rather  than  attempt  to  do  the  work  one's  self  with  the 
attending  difficulty  of  preparing  insecticides  and  securing  apparatus 
for  work  on  a  comparatively  small  scale.  In  California  this  is  a  com- 
mon practice,  and  also  in  some  of  our  Eastern  cities,  and  has  worked 
excellently. 

DETERMINATION   OF   THE   RESULT   OF   TREATMENT. 

It  is  often  of  imjjortance  to  know  when  and  how  to  determine  the 
effect  of  any  treatment  applied  directly  to  insects  exposed  on  the  sur- 
face of  plants.  In  the  case  of  scale  insects,  especially  during  the  dor- 
mant condition  in  winter,  the  response  to  insecticides  is  very  slow  and 
gradual.  The  scale  larvas,  or  any  young  scales  during  the  growing 
season,  are  killed  in  a  few  minutes,  or  a  few  hours  at  furthest,  just 
as  any  other  soft-bodied  insect,  but  the  mature  scale  does  not  usually 
127 


46 

exhibit  the  eflfects  of  the  wash  or  gas  for  some  time.  Little  can  be 
judged,  ordinarily,  of  the  ultimate  results  before  two  weeks,  and  itis 
often  necessaiy  to  wait  one  or  even  two  months  to  get  final  conclu- 
sions. In  the  case  of  liquid  washes  the  slow  progressive  death  of  the 
scales  is  apparently  due  to  the  gradual  penetration  of  the  insecticide, 
and  also  to  the  softening  and  loosening  of  the  scale  itself,  enabling 
subsequent  weather  conditions  of  moisture  and  cold  to  be  more  fatal. 

With  such  biting  insects  as  caterpillars  and  slug  worms,  after  treat- 
ment with  arsenicals  or  other  poisons  death  rapidly  follows,  the  time 
being  somewhat  in  proportion  to  the  size  of  the  larvas  and  their 
natural  vigor.  Soft-bodied  larva?,  such  as  the  slug  worms  and  very 
young  larvaj  of  moths  and  beetles  or  other  insects,  are  killed  in  a  day 
or  two.  Large  and  strong  larvge  sometimes  survive  the  effect  of 
poison  for  eight  or  ten  days,  and  leaf -feeding  beetles  will  often  fly 
away  and  perish  from  the  poison  in  their  places  of  concealment. 

Many  larvae  or  other  forms  of  leaf-feeding  insects,  after  taking  one 
or  tAvo  meals  of  poisoned  foliage,  wnll  remain  in  a  semitorpid  and 
diseased  condition  on  the  plants  for  several  days  before  they  finally 
succumb.  The  protection  to  the  plant,  however,  is  just  as  great  as 
though  the}^  had  died  immediately,  but  misapprehension  may  often 
arise  and  the  poison  may  be  deemed  to  have  been  of  no  service. 

The  complete  extermination  of  insects  on  plants  is  often  a  very 
difficult,  if  not  an  impossible  undertaking.  This  is  especially  true  of 
scale  insects.  In  California  even,  where  the  work  against  these 
enemies  of  fruits  has  been  most  thorough  and  successful,  experience 
has  shown  that  the  best  that  can  be  done  is  a  practical  elimination  of 
the  scale  for  the  time  being,  and  it  is  often  necessary  to  repeat  the 
treatment  every  year  or  two.  In  exceptional  cases  once  in  three  years 
suffices.  With  leaf-feeding  insects  it  is  often  possible  to  effect  com- 
plete extermination  with  the  use  of  arsenical  poisons.  Such  sucking 
insects  as  aphides  may  also  be  completely  exterminated.  But  in  gen- 
eral all  applications  or  methods  of  treatment  must  be  recognized, 
more  or  less,  as  a  continuous  charge  on  the  crop,  as  much  so  as  are 
the  ordinary  cultural  operations. 

CONTROL  OF  INSECTS  BY  CULTURAL  METHODS. 

It  is  much  easier  to  ward  off  an  attack  of  insects  or  to  make  condi- 
tions unfavorable  for  their  multiplication  than  to  destroy  them  after 
they  are  once  in  possession;  and  in  controlling  them,  methods  and 
systems  of  farm  and  orchard  culture  have  long  been  recognized  as  of 
the  greatest  value,  more  so  even  than  the  employment  of  insecticides, 
which,  in  most  cases,  can  onl}'^  stop  an  injury  already  begun.  Insects 
thrive  on  neglect,  multiply  best  in  land  seldom  or  never  cultivated, 
and  winter  over  in  rubliish,  prunings,  or  the  undisturbed  soil  about 
their  food  plants,  and  become,  under  these  conditions,  more  numerous 

127 


47 

every  year.  It  is  a  fact  of  common  observation  that  it  is  the  neglected 
farfn,  vineyard,  or  orchard  filled  with  weeds  or  wild  growth  which  is 
certain  to  be  stocked  with  all  the  principal  insect  enemies;  and,  on  the 
other  hand,  thorough  and  constant  culture,  with  the  removal  and 
burning  of  prunings,  stubble,  and  other  waste,  the  collection  and  de- 
struction of  fallen  and  diseased  fruit,  and  the  practice,  where  possible, 
of  fall  plowing  to  disturb  the  hibernating  quarters  of  field  insects, 
will  almost  certainly  be  accompanied  by  comparative  immunity  from 
insect  pests. 

The  vigor  and  healthfulness  of  plant  growth  has  also  much  to  do 
with  freedom  from  insect  injury.  Strong,  healthy  j)lants  seem  to  have 
a  native  power  of  resistance  which  renders  them,  in  a  measure,  dis- 
tasteful to  most  insects,  or  at  least  able  to  throw  off  or  withstand  their 
attacks.  A  plant  already  weakened  from  any  cause,  however,  seems 
to  be  especially  sought  after,  is  almost  sure  to  be  the  first  affected, 
and  furnishes  a  starting  point  for  general  infestation.  Anything, 
therefore,  which  aids  good  culture  in  keeping  plants  strong  and 
vigorous,  such  as  the  judicious  use  of  fertilizers,  will  materially 
assist  in  preventing  injury. 

The  constant  cropping  of  large  areas  of  land  year  after  year  to 
the  same  staple  is  largely  responsible  for  the  excessive  loss  from  in- 
sects in  this  country  as  compared  with  European  countries,  because 
this  practice  furnishes  the  best  possible  conditions  for  the  multiplica- 
tion of  the  enemies  of  such  crops.  A  most  valuable  cultural  means, 
therefore,  is  a  system  of  rotation  of  crops  which  will  prevent  the 
gradual  yearly  increase  of  the  enemies  of  any  particular  staple  by 
the  substitution  every  year  or  two  of  other  cultures  not  subject  to  the 
attacks  of  the  insect  enemies  of  the  first. 

With  such  insects  as  the  Hessian  fly,  the  squash  borers,  and  many 
others  which  have  regular  times  of  appearance,  much  can  be  done 
by  the  planting  of  early  or  late  varieties  or  by  deferring  seeding 
so  as  to  avoid  the  periods  of  excessive  danger.  Wherever  possible, 
varieties  should  be  selected  which  experience  has  shown  to  be  re- 
sistant to  insect  attack.  Familiar  illustrations  of  such  resistant  va- 
rieties in  all  classes  of  cultivated  plants  will  occur  to  every  practical 
man,  and  a  better  instance  of  the  benefit  to  be  derived  from  taking 
advantage  of  this  knowledge  can  not  be  given  than  the  almost  uni- 
versal adoption  of  resistant  American  vines  as  stocks  for  the  regenera- 
tion of  the  vineyards  of  France  destroyed  by  the  phylloxera  and  for 
the  similarly  affected  vineyards  of  European  grapes  in  California. 

In  the  case  of  stored-grain  pests,  particularly  the  Angoumois  moth, 
or  so-called  "  fly  weevil,"  the  chief  danger  in  the  South  occurs  while 
the  grain  is  standing  in  shock  or  stack,  after  harvesting,  during  which 
period  the  insects  have  easy  access  to  it.  This  source  of  infestation 
may  be  avoided  by  thrashing  grain  promptly  after  harvesting  and 
storing  it  in  bulk.    This  wall  prevent  injury  to  more  than  the  sur- 

127 


48 

face  larer,  as  the  insects  are  not  likely  to  penetrate  deeply  into  the 
mass  of  the  grain. 

These  general  notes  are  by  no  means  new,  but  their  importance  jus- 
tifies their  repetition,  as  indicating  the  best  preventive  measures  in 
connection  with  the  remedial  ones  already  given. 

THE  PROFIT  IN  REMEDIAL  MEASURES. 

The  overwhelming  experience  of  the  past  twenty  years  makes  it 
almost  unnecessary  to  urge,  on  the  ground  of  pecuniary  returns,  the 
adoption  of  the" measures  re^mmended  in  the  foregoing  pages  against 
insects.  To  emphasize  the  value  of  such  practice  it  is  only  necessary 
to  call  attention  to  the  fact  that  the  loss  to  orchard,  garden,  and  farm 
crops  frequently  amounts  to  from  15  to  75  per  cent  of  the  entire 
product,  and  innumerable  instances  could  be  pointed  out  where  such 
lo^s  has  been  sustained  year  after  year,  while  now,  by  the  adoption  of 
remedial  measures,  large  yields  are  regularly  secured  with  an  insig- 
nificant expenditure  for  treatment.  It  has  been  established  that  in 
the  case  of  the  apple  crop  spraying  will  protect  from  50  to  75  per 
cent  of  the  fruit  which  would  otherwise  be  wormy,  and  that  in  actual 
marketing  experience  the  price  has  been  enhanced  from  $1  to  $2.50 
per  barrel,  and  this  at  a  cost  of  only  about  10  cents  per  tree  for  labor 
and  material.  This  is  especially  true  of  regions  where  the  codling 
moth  has  but  one  full  brood  annually. 

In  the  case  of  one  orchard  in  Virginia,  only  one-third  of  which  was 
sprayed,  the  result  was  an  increase  in  the  A'ield  of  sound  fruit  in  the 
portion  treated  of  nearly  50  per  cent,  and  an  increase  of  the  value  of 
this  fruit  over'tlie  rest  of  100  per  cent.  The  loss  from  not  having 
treated  the  other  two-thirds  was  estimated  at  $2,500.  The  saving  to 
the  plum  crop  and  other  small  fruits  frequently  amounts  to  the  secur- 
ing of  a  perfect  crop  where  otherwise  no  yield  whatever  of  sound 
fruit  could  be  secured. 

An  illustration  in  the  case  of  field  insects  may  also  be  given  where, 
by  the'  ad;option  of  a  system  of  rotation,  in  which  oats  were  made  to 
alternate  with  corn,  the  owner  of  a  large  farm  in  Indiana  made  a 
saving  of  $10,000  per  year,  this  amount  representing  the  loss  pre- 
viously sustained  annually  from  the  corn  rootv.'orm.  The  cotton  crop, 
which  formerly  in  years  of  bad  infestation  by  the  leaf  worm  was 
estimated  to  be  injured  to  the  extent  of  $30,000,000,  is  now  compara- 
tively free  from  such  injury,  owing  to  the  general  use  of  arsenicals. 

Facts  of  like  import  could  be  addu<}ed  in  regard  to  many  other 
leading  staples,  but  the  foregoing  are  sufficient  to  emj^hasize  the 
money  value  of  intelligent  action  against  insect  enemies,  which  may 
often  represent  the  difference  between  a  profit  and  a  loss  in  agricul- 
tural operations. 

127 

o 


